Help near Springfield, MO

[Tom Lins]

> Tom
>
> Have you called Blacklister Randy VanW in Battlefield, Mo?
> He's very GMC capable.
>
> Dennis
>
>

> > Right after I sent the email to bdub a Missouri Trooper stopped to help us.
> > He called a local tow company for us since we were partialy blocking a lane.
> > The tow company figured out the problem.
> > The fuel filter was totally clogged next to the electric fuel pump which was also barely moving any fuel after they replaced the filter.
> > Also the battery was in poor shape which they replaced. (I had to use the boost switch to start the coach)
> > During the drive from their shop to the campground I noticed the voltage is showing 11 volts so I believe the alternator needs replacing
> > too.
> >
> > I looked at the parts interchange online and the Autozone alternator part number in the online version comes up as a starter not an
> > alternator.
> > Does anyone have a good Autozone part number?
> > I searched Autozone for 77 Toranado alternator and I want to make sure.
> >
> > And thanks bdub for the relay to the net.

No I did not
Silly me I did not bring it with me. Printed it out and then forgot it on my desk.

--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[Tom Lins]

> Right after I sent the email to bdub a Missouri Trooper stopped to help us.
> He called a local tow company for us since we were partialy blocking a lane.
> The tow company figured out the problem.
> The fuel filter was totally clogged next to the electric fuel pump which was also barely moving any fuel after they replaced the filter.
> Also the battery was in poor shape which they replaced. (I had to use the boost switch to start the coach)
> During the drive from their shop to the campground I noticed the voltage is showing 11 volts so I believe the alternator needs replacing too.
>
> I looked at the parts interchange online and the Autozone alternator part number in the online version comes up as a starter not an alternator.
> Does anyone have a good Autozone part number?
> I searched Autozone for 77 Toranado alternator and I want to make sure.
>
> And thanks bdub for the relay to the net.

Ok now I am puzzled. I got the replacement alternator in and when I start up the volt meter shows about 11 to 11.5 volts. Shouldn't I be reading 14 or
so?
Could it be that the PO hooked the guage in such a manner that it is only reading 11 when everything is ok?

--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[tom1]

Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode isolator pack
(I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I think.

Tom
--
Tom

77 Kingsley. Mostly Stock, 455, Quad bag, tachometer, 16"wheels, Macerator.
Southern California, huntington beach

 

[Randy Van Winkle]

> Ok now I am puzzled. I got the replacement alternator in and when I start up the volt meter shows about 11 to 11.5 volts. Shouldn't I be reading
> 14 or so?
> Could it be that the PO hooked the guage in such a manner that it is only reading 11 when everything is ok?

Do you have a handheld volt meter you could check voltage at the battery (or at the center terminal of the isolator)? This would tell you whether the
battery is getting charged. It is possible there is a voltage drop somewhere that the installed meter is reading. Also possible that the sense or
exciter wire is not wired properly causing alternator to not start charging.
--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO

 

[Ken B]

> Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode isolator
> pack (I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I think.
>
> Tom


Tom is entirely correct here is some more info.

Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the aluminum plate that the isolator is mounted on for your negative meter lead
connection. Any cheap volt meter will work. (Harbor Freight, Walmart, Sears, etc.) The center terminal of the isolator should read around 14.7
volts. The top and bottom terminals should read around 14.0 volts.

If those voltages are correct read the voltage across the battery. It also should be around 14.0 volts.

Without the above voltage numbers, here are my best guesses.
1. Loose plug in back of the alternator
2. Bad replacement alternator.
3. Bad isolator
4. Blown fusible link
5. Blown "GEN" light in the dash causing the alternator not to start. Does the GEN light turn on with the key on and prior to starting?

Good Luck. The above are just guesses until we get more information.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Tom Lins]

> > Ok now I am puzzled. I got the replacement alternator in and when I start up the volt meter shows about 11 to 11.5 volts. Shouldn't I be
> > reading 14 or so?
> > Could it be that the PO hooked the guage in such a manner that it is only reading 11 when everything is ok?
>
> Do you have a handheld volt meter you could check voltage at the battery (or at the center terminal of the isolator)? This would tell you whether
> the battery is getting charged. It is possible there is a voltage drop somewhere that the installed meter is reading. Also possible that the sense
> or exciter wire is not wired properly causing alternator to not start charging.

Had to go get a VOM (another thing that is sitting on my desk)and checked the voltage at the center post of the isolator and there is a little over 14
volts with the engine running. so it appears there is another thing on the list to check when we get home. The voltage gauge on the dash needs to be
rewired.

The DL7157 from AZ is a rebuilt Delco-Remy, don't know if they all are but this one was.

All is well, now we can start for home in the morning.

Thanks to all for the replies.


--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[Tom Lins]

> > Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode
> > isolator pack (I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I think.
> >
> > Tom
>
>
> Tom is entirely correct here is some more info.
>
> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the aluminum plate that the isolator is mounted on for your negative meter lead
> connection. Any cheap volt meter will work. (Harbor Freight, Walmart, Sears, etc.) The center terminal of the isolator should read around 14.7
> volts. The top and bottom terminals should read around 14.0 volts.
>
> If those voltages are correct read the voltage across the battery. It also should be around 14.0 volts.
>
> Without the above voltage numbers, here are my best guesses.
> 1. Loose plug in back of the alternator
> 2. Bad replacement alternator.
> 3. Bad isolator
> 4. Blown fusible link
> 5. Blown "GEN" light in the dash causing the alternator not to start. Does the GEN light turn on with the key on and prior to starting?
>
> Good Luck. The above are just guesses until we get more information.

Ken

The voltages were all about what you are saying are correct
I really think the dash gauge was not wired correctly, The PPO installed CIP deluxe dash
the one with the 4 gauges either side of the Speedo and Tach and I am not 100% convinced everything is
wired correctly. There are several other switches on the side panel for the 2 large electric fans
in front of the radiator and one to trigger the halon fire extinguisher by the engine.

He also installed a second air compressor in the Electro Level system that needs to be turned on
with a separate switch and it appears to be hooked to the house battery system.
The EL system is acting odd and only seems to be able to maintain normal ride height
As long as it can do that until we get home I will look at that when we get home.

And yes the gen light does come on before you start it.

--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[Ken B]

> > > Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode
> > > isolator pack (I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I
> > > think.
> > >
> > > Tom
> >
> >
> > Tom is entirely correct here is some more info.
> >
> > Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the aluminum plate that the isolator is mounted on for your negative meter lead
> > connection. Any cheap volt meter will work. (Harbor Freight, Walmart, Sears, etc.) The center terminal of the isolator should read around 14.7
> > volts. The top and bottom terminals should read around 14.0 volts.
> >
> > If those voltages are correct read the voltage across the battery. It also should be around 14.0 volts.
> >
> > Without the above voltage numbers, here are my best guesses.
> > 1. Loose plug in back of the alternator
> > 2. Bad replacement alternator.
> > 3. Bad isolator
> > 4. Blown fusible link
> > 5. Blown "GEN" light in the dash causing the alternator not to start. Does the GEN light turn on with the key on and prior to starting?
> >
> > Good Luck. The above are just guesses until we get more information.
>
> Ken
>
> The voltages were all about what you are saying are correct
> I really think the dash gauge was not wired correctly, The PPO installed CIP deluxe dash
> the one with the 4 gauges either side of the Speedo and Tach and I am not 100% convinced everything is
> wired correctly. There are several other switches on the side panel for the 2 large electric fans
> in front of the radiator and one to trigger the halon fire extinguisher by the engine.
>
> He also installed a second air compressor in the Electro Level system that needs to be turned on
> with a separate switch and it appears to be hooked to the house battery system.
> The EL system is acting odd and only seems to be able to maintain normal ride height
> As long as it can do that until we get home I will look at that when we get home.
>
> And yes the gen light does come on before you start it.

Did you read the voltage across the battery with the coach running? If you did, what was that voltage? I expect that voltage to be about .7 below
what you read at the center terminal of the isolator.

Everyone needs to get one of these under $2.00 items. Plug it into the cigarette lighter receiptical and see what the voltage is doing either static
or while driving. I have several of them around.

https://www.aliexpress.com/item/2016-NEW-Digital-LED-Car-Truck-System-Battery-Voltmeter-Voltage-Gauge-Volt-Meter-12V-24V/32788670717.html


--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Ken H.]

Thanks for that good link, Ken. I ordered one for each of the kids &
grandkids. The son is an experienced mechanic, the 2 grandson are getting
there; they'll all appreciate them. The daughter and 2 granddaughters are
hopeless -- they need all the help they can get to avoid car problems.

Ken H.

> ​...
>
> Everyone needs to get one of these under $2.00 items. Plug it into the
> cigarette lighter receiptical and see what the voltage is doing either
> static
> or while driving. I have several of them around.
>
> https://www.aliexpress.com/item/2016-NEW-Digital-LED-Car-
> Truck-System-Battery-Voltmeter-Voltage-Gauge-Volt-
> Meter-12V-24V/32788670717.html
> --

 

[Tom Lins]

> > > Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode
> > > isolator pack (I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I
> > > think.
> > >
> > > Tom
> >
> >
> > Tom is entirely correct here is some more info.
> >
> > Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the aluminum plate that the isolator is mounted on for your negative meter lead
> > connection. Any cheap volt meter will work. (Harbor Freight, Walmart, Sears, etc.) The center terminal of the isolator should read around 14.7
> > volts. The top and bottom terminals should read around 14.0 volts.
> >
> > If those voltages are correct read the voltage across the battery. It also should be around 14.0 volts.
> >
> > Without the above voltage numbers, here are my best guesses.
> > 1. Loose plug in back of the alternator
> > 2. Bad replacement alternator.
> > 3. Bad isolator
> > 4. Blown fusible link
> > 5. Blown "GEN" light in the dash causing the alternator not to start. Does the GEN light turn on with the key on and prior to starting?
> >
> > Good Luck. The above are just guesses until we get more information.
>
> Ken
>
> The voltages were all about what you are saying are correct
> I really think the dash gauge was not wired correctly, The PPO installed CIP deluxe dash
> the one with the 4 gauges either side of the Speedo and Tach and I am not 100% convinced everything is
> wired correctly. There are several other switches on the side panel for the 2 large electric fans
> in front of the radiator and one to trigger the halon fire extinguisher by the engine.
>
> He also installed a second air compressor in the Electro Level system that needs to be turned on
> with a separate switch and it appears to be hooked to the house battery system.
> The EL system is acting odd and only seems to be able to maintain normal ride height
> As long as it can do that until we get home I will look at that when we get home.
>
> And yes the gen light does come on before you start it.



Ken

I made a stupid mistake. I measured the voltage with the engine running but forgot I was plugged into shore power
This morning in daylight I tried again with the coach disconnected with the engine running. Up to running temp and idleing
the voltage on the isolater are as follows

Top 11.8
Center 20
Bottom 19.1

Chassis Battery reads 11.8 from the hot to the plate the isolator is mounted to.

Bad isolator?

--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[emerystora]

Shut it down! Way to high voltage on the bottom! You’ll ruin your batttery.

Yes, it looks like a bad isolator.

Emery Stora
77 Kingsley
Frederick, CO

>

>>>> Do you have a hand held voltmeter? If so, I'd check the voltage across the battery and the voltage at the center position of the diode
>>>> isolator pack (I think this is the lead that goes to the alternator). The isolator diodes will give a half a volt or more voltage drop I
>>>> think.
>>>>
>>>> Tom
>>>
>>>
>>> Tom is entirely correct here is some more info.
>>>
>>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the aluminum plate that the isolator is mounted on for your negative meter lead
>>> connection. Any cheap volt meter will work. (Harbor Freight, Walmart, Sears, etc.) The center terminal of the isolator should read around 14.7
>>> volts. The top and bottom terminals should read around 14.0 volts.
>>>
>>> If those voltages are correct read the voltage across the battery. It also should be around 14.0 volts.
>>>
>>> Without the above voltage numbers, here are my best guesses.
>>> 1. Loose plug in back of the alternator
>>> 2. Bad replacement alternator.
>>> 3. Bad isolator
>>> 4. Blown fusible link
>>> 5. Blown "GEN" light in the dash causing the alternator not to start. Does the GEN light turn on with the key on and prior to starting?
>>>
>>> Good Luck. The above are just guesses until we get more information.
>>
>> Ken
>>
>> The voltages were all about what you are saying are correct
>> I really think the dash gauge was not wired correctly, The PPO installed CIP deluxe dash
>> the one with the 4 gauges either side of the Speedo and Tach and I am not 100% convinced everything is
>> wired correctly. There are several other switches on the side panel for the 2 large electric fans
>> in front of the radiator and one to trigger the halon fire extinguisher by the engine.
>>
>> He also installed a second air compressor in the Electro Level system that needs to be turned on
>> with a separate switch and it appears to be hooked to the house battery system.
>> The EL system is acting odd and only seems to be able to maintain normal ride height
>> As long as it can do that until we get home I will look at that when we get home.
>>
>> And yes the gen light does come on before you start it.
>
>
>
> Ken
>
> I made a stupid mistake. I measured the voltage with the engine running but forgot I was plugged into shore power
> This morning in daylight I tried again with the coach disconnected with the engine running. Up to running temp and idleing
> the voltage on the isolater are as follows
>
> Top 11.8
> Center 20
> Bottom 19.1
>
> Chassis Battery reads 11.8 from the hot to the plate the isolator is mounted to.
>
> Bad isolator?
>
> --
> Tom Lins
> Elkton, FL
> 77 GM Rear Twin
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[Jim Hupy]

Tom, you have more wrong than a bad isolator. Center tap and ground should
show 14.5 or so. Both top and bottom taps should show .7 volts less than
that. 20 volts idling tells me that your engine alternator has a bad
internal regulator, OR the sense wires have an open circuit ( those are the
two wires that plug into the alternator ) trace those down and check for
continuity on both of them when they are disconnected from the circuit.
Frequently, they have a second 2 pin connector buried in the wire loom that
goes across the front of the engine near the upper thermostat housing. Age
and heat and vibration all take their toll.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

Shut it down! Way to high voltage on the bottom! You’ll ruin your
batttery.

Yes, it looks like a bad isolator.

Emery Stora
77 Kingsley
Frederick, CO

>

>>>> Do you have a hand held voltmeter? If so, I'd check the voltage
across the battery and the voltage at the center position of the diode
>>>> isolator pack (I think this is the lead that goes to the alternator).
The isolator diodes will give a half a volt or more voltage drop I
>>>> think.
>>>>
>>>> Tom
>>>
>>>
>>> Tom is entirely correct here is some more info.
>>>
>>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the
aluminum plate that the isolator is mounted on for your negative meter lead
>>> connection. Any cheap volt meter will work. (Harbor Freight, Walmart,
Sears, etc.) The center terminal of the isolator should read around 14.7
>>> volts. The top and bottom terminals should read around 14.0 volts.
>>>
>>> If those voltages are correct read the voltage across the battery. It
also should be around 14.0 volts.
>>>
>>> Without the above voltage numbers, here are my best guesses.
>>> 1. Loose plug in back of the alternator
>>> 2. Bad replacement alternator.
>>> 3. Bad isolator
>>> 4. Blown fusible link
>>> 5. Blown "GEN" light in the dash causing the alternator not to start.
Does the GEN light turn on with the key on and prior to starting?
>>>
>>> Good Luck. The above are just guesses until we get more information.
>>
>> Ken
>>
>> The voltages were all about what you are saying are correct
>> I really think the dash gauge was not wired correctly, The PPO installed
CIP deluxe dash
>> the one with the 4 gauges either side of the Speedo and Tach and I am
not 100% convinced everything is
>> wired correctly. There are several other switches on the side panel for
the 2 large electric fans
>> in front of the radiator and one to trigger the halon fire extinguisher
by the engine.
>>
>> He also installed a second air compressor in the Electro Level system
that needs to be turned on
>> with a separate switch and it appears to be hooked to the house battery
system.
>> The EL system is acting odd and only seems to be able to maintain normal
ride height
>> As long as it can do that until we get home I will look at that when we
get home.
>>
>> And yes the gen light does come on before you start it.
>
>
>
> Ken
>
> I made a stupid mistake. I measured the voltage with the engine running
but forgot I was plugged into shore power
> This morning in daylight I tried again with the coach disconnected with
the engine running. Up to running temp and idleing
> the voltage on the isolater are as follows
>
> Top 11.8
> Center 20
> Bottom 19.1
>
> Chassis Battery reads 11.8 from the hot to the plate the isolator is
mounted to.
>
> Bad isolator?
>
> --
> Tom Lins
> Elkton, FL
> 77 GM Rear Twin
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

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[bdub1]

Bad alternator! First. Center isolator post wire comes directly from
alternator. That's off the charts! Internal regulator must be fried.

bdub

> Shut it down! Way to high voltage on the bottom! You’ll ruin your
> batttery.
>
> Yes, it looks like a bad isolator.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

> >

> >>>> Do you have a hand held voltmeter? If so, I'd check the voltage
> across the battery and the voltage at the center position of the diode
> >>>> isolator pack (I think this is the lead that goes to the
> alternator). The isolator diodes will give a half a volt or more voltage
> drop I
> >>>> think.
> >>>>
> >>>> Tom
> >>>
> >>>
> >>> Tom is entirely correct here is some more info.
> >>>
> >>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the
> aluminum plate that the isolator is mounted on for your negative meter lead
> >>> connection. Any cheap volt meter will work. (Harbor Freight, Walmart,
> Sears, etc.) The center terminal of the isolator should read around 14.7
> >>> volts. The top and bottom terminals should read around 14.0 volts.
> >>>
> >>> If those voltages are correct read the voltage across the battery. It
> also should be around 14.0 volts.
> >>>
> >>> Without the above voltage numbers, here are my best guesses.
> >>> 1. Loose plug in back of the alternator
> >>> 2. Bad replacement alternator.
> >>> 3. Bad isolator
> >>> 4. Blown fusible link
> >>> 5. Blown "GEN" light in the dash causing the alternator not to
> start. Does the GEN light turn on with the key on and prior to starting?
> >>>
> >>> Good Luck. The above are just guesses until we get more information.
> >>
> >> Ken
> >>
> >> The voltages were all about what you are saying are correct
> >> I really think the dash gauge was not wired correctly, The PPO
> installed CIP deluxe dash
> >> the one with the 4 gauges either side of the Speedo and Tach and I am
> not 100% convinced everything is
> >> wired correctly. There are several other switches on the side panel for
> the 2 large electric fans
> >> in front of the radiator and one to trigger the halon fire extinguisher
> by the engine.
> >>
> >> He also installed a second air compressor in the Electro Level system
> that needs to be turned on
> >> with a separate switch and it appears to be hooked to the house battery
> system.
> >> The EL system is acting odd and only seems to be able to maintain
> normal ride height
> >> As long as it can do that until we get home I will look at that when we
> get home.
> >>
> >> And yes the gen light does come on before you start it.
> >
> >
> >
> > Ken
> >
> > I made a stupid mistake. I measured the voltage with the engine running
> but forgot I was plugged into shore power
> > This morning in daylight I tried again with the coach disconnected with
> the engine running. Up to running temp and idleing
> > the voltage on the isolater are as follows
> >
> > Top 11.8
> > Center 20
> > Bottom 19.1
> >
> > Chassis Battery reads 11.8 from the hot to the plate the isolator is
> mounted to.
> >
> > Bad isolator?
> >
> > --
> > Tom Lins
> > Elkton, FL
> > 77 GM Rear Twin
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[john phillips]

If the sense wire goes to the chassis battery the isolator would cause the
problem.

> Tom, you have more wrong than a bad isolator. Center tap and ground should
> show 14.5 or so. Both top and bottom taps should show .7 volts less than
> that. 20 volts idling tells me that your engine alternator has a bad
> internal regulator, OR the sense wires have an open circuit ( those are the
> two wires that plug into the alternator ) trace those down and check for
> continuity on both of them when they are disconnected from the circuit.
> Frequently, they have a second 2 pin connector buried in the wire loom that
> goes across the front of the engine near the upper thermostat housing. Age
> and heat and vibration all take their toll.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>
> Shut it down! Way to high voltage on the bottom! You’ll ruin your
> batttery.
>
> Yes, it looks like a bad isolator.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

> >

> >>>> Do you have a hand held voltmeter? If so, I'd check the voltage
> across the battery and the voltage at the center position of the diode
> >>>> isolator pack (I think this is the lead that goes to the alternator).
> The isolator diodes will give a half a volt or more voltage drop I
> >>>> think.
> >>>>
> >>>> Tom
> >>>
> >>>
> >>> Tom is entirely correct here is some more info.
> >>>
> >>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the
> aluminum plate that the isolator is mounted on for your negative meter lead
> >>> connection. Any cheap volt meter will work. (Harbor Freight, Walmart,
> Sears, etc.) The center terminal of the isolator should read around 14.7
> >>> volts. The top and bottom terminals should read around 14.0 volts.
> >>>
> >>> If those voltages are correct read the voltage across the battery. It
> also should be around 14.0 volts.
> >>>
> >>> Without the above voltage numbers, here are my best guesses.
> >>> 1. Loose plug in back of the alternator
> >>> 2. Bad replacement alternator.
> >>> 3. Bad isolator
> >>> 4. Blown fusible link
> >>> 5. Blown "GEN" light in the dash causing the alternator not to start.
> Does the GEN light turn on with the key on and prior to starting?
> >>>
> >>> Good Luck. The above are just guesses until we get more information.
> >>
> >> Ken
> >>
> >> The voltages were all about what you are saying are correct
> >> I really think the dash gauge was not wired correctly, The PPO installed
> CIP deluxe dash
> >> the one with the 4 gauges either side of the Speedo and Tach and I am
> not 100% convinced everything is
> >> wired correctly. There are several other switches on the side panel for
> the 2 large electric fans
> >> in front of the radiator and one to trigger the halon fire extinguisher
> by the engine.
> >>
> >> He also installed a second air compressor in the Electro Level system
> that needs to be turned on
> >> with a separate switch and it appears to be hooked to the house battery
> system.
> >> The EL system is acting odd and only seems to be able to maintain normal
> ride height
> >> As long as it can do that until we get home I will look at that when we
> get home.
> >>
> >> And yes the gen light does come on before you start it.
> >
> >
> >
> > Ken
> >
> > I made a stupid mistake. I measured the voltage with the engine running
> but forgot I was plugged into shore power
> > This morning in daylight I tried again with the coach disconnected with
> the engine running. Up to running temp and idleing
> > the voltage on the isolater are as follows
> >
> > Top 11.8
> > Center 20
> > Bottom 19.1
> >
> > Chassis Battery reads 11.8 from the hot to the plate the isolator is
> mounted to.
> >
> > Bad isolator?
> >
> > --
> > Tom Lins
> > Elkton, FL
> > 77 GM Rear Twin
> >
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
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--

*John Phillips*

 

[Jim Hupy]

That is why I told him that BOTH his isolator, and internal regulator in
the alternator are bad, also told him to check sense wires for continuity
by isolating them and checking each end of both wires. That eliminates any
outside influence from affecting his meter readings. Golly, I hate
supposedly rebuilt aftermarket alternators. So does my rebuilder, but they
bring him a lot of business.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> If the sense wire goes to the chassis battery the isolator would cause the
> problem.
>

>
> > Tom, you have more wrong than a bad isolator. Center tap and ground
> should
> > show 14.5 or so. Both top and bottom taps should show .7 volts less than
> > that. 20 volts idling tells me that your engine alternator has a bad
> > internal regulator, OR the sense wires have an open circuit ( those are
> the
> > two wires that plug into the alternator ) trace those down and check for
> > continuity on both of them when they are disconnected from the circuit.
> > Frequently, they have a second 2 pin connector buried in the wire loom
> that
> > goes across the front of the engine near the upper thermostat housing.
> Age
> > and heat and vibration all take their toll.
> > Jim Hupy
> > Salem, Or
> > 78 GMC ROYALE 403
> >

> >
> > Shut it down! Way to high voltage on the bottom! You’ll ruin your
> > batttery.
> >
> > Yes, it looks like a bad isolator.
> >
> > Emery Stora
> > 77 Kingsley
> > Frederick, CO
> >

> > >

> > >>>> Do you have a hand held voltmeter? If so, I'd check the voltage
> > across the battery and the voltage at the center position of the diode
> > >>>> isolator pack (I think this is the lead that goes to the
> alternator).
> > The isolator diodes will give a half a volt or more voltage drop I
> > >>>> think.
> > >>>>
> > >>>> Tom
> > >>>
> > >>>
> > >>> Tom is entirely correct here is some more info.
> > >>>
> > >>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the
> > aluminum plate that the isolator is mounted on for your negative meter
> lead
> > >>> connection. Any cheap volt meter will work. (Harbor Freight,
> Walmart,
> > Sears, etc.) The center terminal of the isolator should read around 14.7
> > >>> volts. The top and bottom terminals should read around 14.0 volts.
> > >>>
> > >>> If those voltages are correct read the voltage across the battery.
> It
> > also should be around 14.0 volts.
> > >>>
> > >>> Without the above voltage numbers, here are my best guesses.
> > >>> 1. Loose plug in back of the alternator
> > >>> 2. Bad replacement alternator.
> > >>> 3. Bad isolator
> > >>> 4. Blown fusible link
> > >>> 5. Blown "GEN" light in the dash causing the alternator not to
> start.
> > Does the GEN light turn on with the key on and prior to starting?
> > >>>
> > >>> Good Luck. The above are just guesses until we get more information.
> > >>
> > >> Ken
> > >>
> > >> The voltages were all about what you are saying are correct
> > >> I really think the dash gauge was not wired correctly, The PPO
> installed
> > CIP deluxe dash
> > >> the one with the 4 gauges either side of the Speedo and Tach and I am
> > not 100% convinced everything is
> > >> wired correctly. There are several other switches on the side panel
> for
> > the 2 large electric fans
> > >> in front of the radiator and one to trigger the halon fire
> extinguisher
> > by the engine.
> > >>
> > >> He also installed a second air compressor in the Electro Level system
> > that needs to be turned on
> > >> with a separate switch and it appears to be hooked to the house
> battery
> > system.
> > >> The EL system is acting odd and only seems to be able to maintain
> normal
> > ride height
> > >> As long as it can do that until we get home I will look at that when
> we
> > get home.
> > >>
> > >> And yes the gen light does come on before you start it.
> > >
> > >
> > >
> > > Ken
> > >
> > > I made a stupid mistake. I measured the voltage with the engine running
> > but forgot I was plugged into shore power
> > > This morning in daylight I tried again with the coach disconnected with
> > the engine running. Up to running temp and idleing
> > > the voltage on the isolater are as follows
> > >
> > > Top 11.8
> > > Center 20
> > > Bottom 19.1
> > >
> > > Chassis Battery reads 11.8 from the hot to the plate the isolator is
> > mounted to.
> > >
> > > Bad isolator?
> > >
> > > --
> > > Tom Lins
> > > Elkton, FL
> > > 77 GM Rear Twin
> > >
> > >
> > > _______________________________________________
> > > GMCnet mailing list
> > > Unsubscribe or Change List Options:
> > > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> > _______________________________________________
> > GMCnet mailing list
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> >
>
>
>
> --
>
> *John Phillips*
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[emerystora]

The sensing wire from the alternator that controls the internal voltage regulator goes to the engine battery.

If the 11.8 volts he mentions is the engine battery it could mean that the isolator is indeed bad and the low voltage it is providing to that battery is causing the voltage regulator in the alternator to increase to 20 volts in an effort to increase the voltage to the engine battery. So, I still maintain that he has a bad isolator.

Before looking for other causes I would recommend changing the isolator.

A quick check could be to move the center wire on the isolator to the top terminal and checking to see if the voltage changes to the approximately 14 volt level. If it does then it definitely is a bad isolator.

Emery Stora
77 Kingsley
Frederick, CO

>
> Tom, you have more wrong than a bad isolator. Center tap and ground should
> show 14.5 or so. Both top and bottom taps should show .7 volts less than
> that. 20 volts idling tells me that your engine alternator has a bad
> internal regulator, OR the sense wires have an open circuit ( those are the
> two wires that plug into the alternator ) trace those down and check for
> continuity on both of them when they are disconnected from the circuit.
> Frequently, they have a second 2 pin connector buried in the wire loom that
> goes across the front of the engine near the upper thermostat housing. Age
> and heat and vibration all take their toll.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>
> Shut it down! Way to high voltage on the bottom! You’ll ruin your
> batttery.
>
> Yes, it looks like a bad isolator.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

>>

>>>>> Do you have a hand held voltmeter? If so, I'd check the voltage
> across the battery and the voltage at the center position of the diode
>>>>> isolator pack (I think this is the lead that goes to the alternator).
> The isolator diodes will give a half a volt or more voltage drop I
>>>>> think.
>>>>>
>>>>> Tom
>>>>
>>>>
>>>> Tom is entirely correct here is some more info.
>>>>
>>>> Read the voltage at the isolator WITH THE ENGINE RUNNING. Use the
> aluminum plate that the isolator is mounted on for your negative meter lead
>>>> connection. Any cheap volt meter will work. (Harbor Freight, Walmart,
> Sears, etc.) The center terminal of the isolator should read around 14.7
>>>> volts. The top and bottom terminals should read around 14.0 volts.
>>>>
>>>> If those voltages are correct read the voltage across the battery. It
> also should be around 14.0 volts.
>>>>
>>>> Without the above voltage numbers, here are my best guesses.
>>>> 1. Loose plug in back of the alternator
>>>> 2. Bad replacement alternator.
>>>> 3. Bad isolator
>>>> 4. Blown fusible link
>>>> 5. Blown "GEN" light in the dash causing the alternator not to start.
> Does the GEN light turn on with the key on and prior to starting?
>>>>
>>>> Good Luck. The above are just guesses until we get more information.
>>>
>>> Ken
>>>
>>> The voltages were all about what you are saying are correct
>>> I really think the dash gauge was not wired correctly, The PPO installed
> CIP deluxe dash
>>> the one with the 4 gauges either side of the Speedo and Tach and I am
> not 100% convinced everything is
>>> wired correctly. There are several other switches on the side panel for
> the 2 large electric fans
>>> in front of the radiator and one to trigger the halon fire extinguisher
> by the engine.
>>>
>>> He also installed a second air compressor in the Electro Level system
> that needs to be turned on
>>> with a separate switch and it appears to be hooked to the house battery
> system.
>>> The EL system is acting odd and only seems to be able to maintain normal
> ride height
>>> As long as it can do that until we get home I will look at that when we
> get home.
>>>
>>> And yes the gen light does come on before you start it.
>>
>>
>>
>> Ken
>>
>> I made a stupid mistake. I measured the voltage with the engine running
> but forgot I was plugged into shore power
>> This morning in daylight I tried again with the coach disconnected with
> the engine running. Up to running temp and idleing
>> the voltage on the isolater are as follows
>>
>> Top 11.8
>> Center 20
>> Bottom 19.1
>>
>> Chassis Battery reads 11.8 from the hot to the plate the isolator is
> mounted to.
>>
>> Bad isolator?
>>
>> --
>> Tom Lins
>> Elkton, FL
>> 77 GM Rear Twin
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[Ken B]

OK, You have a bad isolator. The voltage on the center terminal is high because that alternator is sensing the low voltage on the engine side and
trying to make up for it.

The alternator is probably ok.

More to follow in a second note.

Ken B.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Ken B]

At this point you have several options:

1.Replace the isolator with one rated at 80 amps or higher.

2. If you just want to get going down the road and fix it later, move the wire on the center terminal of the isolator to the top terminal along with
the wire that is already there. This will supply alternator voltage to the engine battery and the voltage should come down to something around 14.0
on the engine side only. It will NOT charge the house battery this way from the alternator.

3. Reversing the wires on the top and bottom terminals of the isolator will accomplish the same thing as item 2 above.

If you want to charge the house battery while driving home using #2 or #3 above. Add a short jumper wire 16 or 18 gauge between the top and bottom
terminals ONLY WHILE DRIVING. Disconnect it when parked for the evening to prevent one battery from discharging the other one. Assuming that both
batteries (house and engine) are good then leaving it connected for short periods of time while refueling will not hurt anything.

If you do #2 or #3 above please recheck the voltages at the isolator to make sure nothing is going over +15 volts.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Tom Lins]

> The sensing wire from the alternator that controls the internal voltage regulator goes to the engine battery.
>
> If the 11.8 volts he mentions is the engine battery it could mean that the isolator is indeed bad and the low voltage it is providing to that
> battery is causing the voltage regulator in the alternator to increase to 20 volts in an effort to increase the voltage to the engine battery. So, I
> still maintain that he has a bad isolator.
>
> Before looking for other causes I would recommend changing the isolator.
>
> A quick check could be to move the center wire on the isolator to the top terminal and checking to see if the voltage changes to the approximately
> 14 volt level. If it does then it definitely is a bad isolator.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO

Ok I moved the center wire to the top post (which is the chassis battery) and it is showing 14.5 volts with the
engine running so it appears the problem is the isolater and luckily Oreilly has a 70 amp isolater and a 150 amp
in stock
If i remember from the is the 70 amp adequate?

--
Tom Lins
Elkton, FL
77 GM Rear Twin

 

[brian krikorian]

Okay.... with all this alternator and isolator talk, I have a question:

On my coach, when I drive under 55, the voltage meter is at about 12-14 (I have one of those that plugs in the cigarette lighter, along with the stock
gauge, and another one on a panel of switches).

When I hit 55 + the thing goes up to 17ish. I've been debating with my mechanic/friend who helps me out whether the alternator is bad. The last time
I had him look at it, they thought it was the isolator and replaced it, and thought that would fix it--but it still would hit 16 to 18 on high speeds.
I began debating maybe it's a bad voltage regulator.

So on my most recent trip, I noticed something new. When I turn on the headlights, it drops down to 10-12 and stays about there. Interestingly
though, if I'm driving city streets at night (below 50mph) my battery starts to drain.

So I'm still thinking alternator is bad. I've switched out the battery as well, and it holds a charge on my garage shelf.

Any thoughts?
--
Brian K
1977 Eleganza II, TZE167V100261
Bellevue, WA
Rebuilt 455, New brake system, a lot of Original Equipment ready to fall apart (discovering more as I go along....)