ONAN starting

B

bill shourt

New member
Oct 2, 2005
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Onan starter stays engaged after engine starts occasionally, usually when cold. When I pull the connector off the start solenoid it disengages
immediatly. Voltage to starter is 12 volts when starting and drops to 8 volts when running. When I pull the wire off starter it drops to 0. If i put
wire back on 0 volts and no starter running.
33 volts across 5 and 8 when running
New dino board, it did this occasionaly with the old board also, but rarely.
New K1 relay
metered across 12 pin connector, 0 or .1 ohms on all connectors.
battery charger out of circuit.
Any ideas for more things to check?
--
Bill and Michele Shourt
78 Kingsley, origional
 
If you are starting it from inside the coach, I would suspect the rocker
start/stop switch contacts or the multi-pin connector behind-underneath the
ONAN. If you are starting it from the control board on the ONAN, I would
inspect the rocker switch on the board, the starter solenoid, the bendix
drive on the starter. Think "things that move". They are subject to dirt,
corrosion, wear.
JWIWD.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

> Onan starter stays engaged after engine starts occasionally, usually when
> cold. When I pull the connector off the start solenoid it disengages
> immediatly. Voltage to starter is 12 volts when starting and drops to 8
> volts when running. When I pull the wire off starter it drops to 0. If i
> put
> wire back on 0 volts and no starter running.
> 33 volts across 5 and 8 when running
> New dino board, it did this occasionaly with the old board also, but
> rarely.
> New K1 relay
> metered across 12 pin connector, 0 or .1 ohms on all connectors.
> battery charger out of circuit.
> Any ideas for more things to check?
> --
> Bill and Michele Shourt
> 78 Kingsley, origional
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Thanks Jim. I have checked both switches, it does it from either one. Starter is rebuilt and it disengages when the wire is pulled from the solenoid. The four pin connector is gone and the wires have been soldered and shrink wrapped .
Driving me nuts.

Sent from my iPad

>
> If you are starting it from inside the coach, I would suspect the rocker
> start/stop switch contacts or the multi-pin connector behind-underneath the
> ONAN. If you are starting it from the control board on the ONAN, I would
> inspect the rocker switch on the board, the starter solenoid, the bendix
> drive on the starter. Think "things that move". They are subject to dirt,
> corrosion, wear.
> JWIWD.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403
>

>>
>> Onan starter stays engaged after engine starts occasionally, usually when
>> cold. When I pull the connector off the start solenoid it disengages
>> immediatly. Voltage to starter is 12 volts when starting and drops to 8
>> volts when running. When I pull the wire off starter it drops to 0. If i
>> put
>> wire back on 0 volts and no starter running.
>> 33 volts across 5 and 8 when running
>> New dino board, it did this occasionaly with the old board also, but
>> rarely.
>> New K1 relay
>> metered across 12 pin connector, 0 or .1 ohms on all connectors.
>> battery charger out of circuit.
>> Any ideas for more things to check?
>> --
>> Bill and Michele Shourt
>> 78 Kingsley, origional
>>
>> _______________________________________________
>> 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
 
My old Onan (before I replaced it) was doing that. The problem turned out to be a short between one of the solenoid wires and the + terminal from the
battery. I replaced the terminal on that wire and the problem was solved. That doesn't sound like your problem, but you might check the connections
on the starter solenoid one more time.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
 
Thanks Carl, will check in the morning.

Sent from my iPad

>
> My old Onan (before I replaced it) was doing that. The problem turned out to be a short between one of the solenoid wires and the + terminal from the
> battery. I replaced the terminal on that wire and the problem was solved. That doesn't sound like your problem, but you might check the connections
> on the starter solenoid one more time.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
In the following I am assuming that when this failure occurs that the engine has started and is running. If it is not running then ignore the
following:

It should not be the switch because K1's power should be dropped the moment the engine starts. Even if you are still holding the switch down. This
is because there is a N/C K2 contact in the circuit. K2 picks up from the Onan Alternator when the alternator reaches 28 + volts AC. This happens
within a second or so of the engine starting to run.

If the engine is not running, then you need to go look at the start and stop switch(es) and cabling.

The start circuit is simple. The start switch(es) simply ground K1 which applies power to the starter and also picks K3 to supply power to the
ignition and fuel pump.

I'm a little confused by the voltage readings that you posted. If K1 is energized, then the coil terminal should read 0 volts (to ground). If the K1
coil is not energized then the K1 coil terminal should read battery voltage which is around +12 volts.

The 8 volt reading that you mentioned means that you have something with a partial short or a short through another component to ground.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> In the following I am assuming that when this failure occurs that the
> engine has started and is running. If it is not running then ignore the
> following:
>
> It should not be the switch because K1's power should be dropped the
> moment the engine starts. Even if you are still holding the switch down.
> This


Read here
http://gmc49ers.blogspot.com/2016/04/onan-start-relay-k1.html

> is because there is a N/C K2 contact in the circuit. K2 picks up from the
> Onan Alternator when the alternator reaches 28 + volts AC. This happens
> within a second or so of the engine starting to run.
>
>
> If the engine is not running, then you need to go look at the start and
> stop switch(es) and cabling.
>
> The start circuit is simple. The start switch(es) simply ground K1 which
> applies power to the starter and also picks K3 to supply power to the
> ignition and fuel pump.
>
> I'm a little confused by the voltage readings that you posted. If K1 is
> energized, then the coil terminal should read 0 volts (to ground). If the
> K1
> coil is not energized then the K1 coil terminal should read battery
> voltage which is around +12 volts.
>
> The 8 volt reading that you mentioned means that you have something with a
> partial short or a short through another component to ground.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://bdub.net/gmcmotorhome.info/
Alternator Protection Cable
http://bdub.net/gmcmotorhome.info/APC.html
 
Ken the Onan is running and the flywheel alternator is putting out 33 VAC the voltage to the solenoid drops to 8 VDC FROM 12 VDC which is enough to hold in solenoid. When I pull the wire off volts drop to 0 VDC. I put the wire back on and no starter running. I think you may be right about partial short to ground. Could it be in the solenoid?

Sent from my iPad

>

>>
>> In the following I am assuming that when this failure occurs that the
>> engine has started and is running. If it is not running then ignore the
>> following:
>>
>> It should not be the switch because K1's power should be dropped the
>> moment the engine starts. Even if you are still holding the switch down.
>> This
>
>
> Read here
> http://gmc49ers.blogspot.com/2016/04/onan-start-relay-k1.html
>
>
>
>> is because there is a N/C K2 contact in the circuit. K2 picks up from the
>> Onan Alternator when the alternator reaches 28 + volts AC. This happens
>> within a second or so of the engine starting to run.
>>
>>
>> If the engine is not running, then you need to go look at the start and
>> stop switch(es) and cabling.
>>
>> The start circuit is simple. The start switch(es) simply ground K1 which
>> applies power to the starter and also picks K3 to supply power to the
>> ignition and fuel pump.
>>
>> I'm a little confused by the voltage readings that you posted. If K1 is
>> energized, then the coil terminal should read 0 volts (to ground). If the
>> K1
>> coil is not energized then the K1 coil terminal should read battery
>> voltage which is around +12 volts.
>>
>> The 8 volt reading that you mentioned means that you have something with a
>> partial short or a short through another component to ground.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://bdub.net/gmcmotorhome.info/
> Alternator Protection Cable
> http://bdub.net/gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Thanks Gene, K1 is wired like the picture. It is new Onan unit from Jim K. It was doing the same thing with the old one but it is doing it more often all the time.

Sent from my iPad

>

>>
>> In the following I am assuming that when this failure occurs that the
>> engine has started and is running. If it is not running then ignore the
>> following:
>>
>> It should not be the switch because K1's power should be dropped the
>> moment the engine starts. Even if you are still holding the switch down.
>> This
>
>
> Read here
> http://gmc49ers.blogspot.com/2016/04/onan-start-relay-k1.html
>
>
>
>> is because there is a N/C K2 contact in the circuit. K2 picks up from the
>> Onan Alternator when the alternator reaches 28 + volts AC. This happens
>> within a second or so of the engine starting to run.
>>
>>
>> If the engine is not running, then you need to go look at the start and
>> stop switch(es) and cabling.
>>
>> The start circuit is simple. The start switch(es) simply ground K1 which
>> applies power to the starter and also picks K3 to supply power to the
>> ignition and fuel pump.
>>
>> I'm a little confused by the voltage readings that you posted. If K1 is
>> energized, then the coil terminal should read 0 volts (to ground). If the
>> K1
>> coil is not energized then the K1 coil terminal should read battery
>> voltage which is around +12 volts.
>>
>> The 8 volt reading that you mentioned means that you have something with a
>> partial short or a short through another component to ground.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://bdub.net/gmcmotorhome.info/
> Alternator Protection Cable
> http://bdub.net/gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I am sitting here looking at the Onan Wiring diagram that Colonel Ken made. +12 volts should always be on one side of the coil. The Onan board
controls the K1 coil by applying ground (-12vdc) on the opposite side of the coil. There is one wire from the K1 coil to pin 7 on the Onan board.
There should be no other wiring connections to either the coil terminal or pin 7 on the Onan board.

That said, Pin 7 on the Onan board goes only to the N/C point of K2 and no where else. So when K2 is powered by the 33VAC from the alternator, the
K2 N/C point should open up and block any path to the ground side of K1. So at this point I would suggest that you have a wiring error, or a short on
the board, or a tacked relay point on K2. Even if you had a tacked relay point, the voltage should drop to K1 when you remove your finger from both
of the starting switches.

I guess that there is a possibility that there could be a worn spot on the coil that when energized the armature might short to. I have never seen
this but it is the only idea that I have right now on what could be causing this problem. That is just a wild guess because I have never seen of or
heard of this failure.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
As Ken posted, there should be 12 volts (battery voltage) on the K1 terminal, not 8. This is a common positive relay and the relay action is activated
by a switched ground. What happens when you remove the grounding wire? Why is there only 8 volts on the power feed? Measure the resistance to ground
on that ground trigger wire after it starts and then you remove it. If removing it does not stop the starter, then there is a ground leak right there
at the relay. If the starter stops, check that wire and circuit for a ground leak with your multimeter or test light. If you have 8 volts on THAT
wire, then it must be the difference between 8 and 12 that is keeping the relay triggered.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Thanks Ken, there is only one wire running from K1 to pin 7 on the control board. It is connected to the left terminal as referenced in picture Mr Fisher sent.
Just started again and had .2VDC on K1 after engine started running, 12.6 before with starter still engaged. Pulled wire from starter solenoid and starter stops. Shut down and restarts starter stops on its own and beautiful Onan just purrs along.
Seems to disengage when warmer, seems to be happening more often.
Worn spot on coil in starter?

Sent from my iPad

>
> I am sitting here looking at the Onan Wiring diagram that Colonel Ken made. +12 volts should always be on one side of the coil. The Onan board
> controls the K1 coil by applying ground (-12vdc) on the opposite side of the coil. There is one wire from the K1 coil to pin 7 on the Onan board.
> There should be no other wiring connections to either the coil terminal or pin 7 on the Onan board.
>
> That said, Pin 7 on the Onan board goes only to the N/C point of K2 and no where else. So when K2 is powered by the 33VAC from the alternator, the
> K2 N/C point should open up and block any path to the ground side of K1. So at this point I would suggest that you have a wiring error, or a short on
> the board, or a tacked relay point on K2. Even if you had a tacked relay point, the voltage should drop to K1 when you remove your finger from both
> of the starting switches.
>
> I guess that there is a possibility that there could be a worn spot on the coil that when energized the armature might short to. I have never seen
> this but it is the only idea that I have right now on what could be causing this problem. That is just a wild guess because I have never seen of or
> heard of this failure.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Terry the 8 volts is on the wire from K1 to starter solenoid when engine is running. The 8 volts drops to 0 when wire is pulled from solenoid and starter disengages. Measured on wire to solenoid.

Sent from my iPad

>
> As Ken posted, there should be 12 volts (battery voltage) on the K1 terminal, not 8. This is a common positive relay and the relay action is activated
> by a switched ground. What happens when you remove the grounding wire? Why is there only 8 volts on the power feed? Measure the resistance to ground
> on that ground trigger wire after it starts and then you remove it. If removing it does not stop the starter, then there is a ground leak right there
> at the relay. If the starter stops, check that wire and circuit for a ground leak with your multimeter or test light. If you have 8 volts on THAT
> wire, then it must be the difference between 8 and 12 that is keeping the relay triggered.
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
If you are pulling the wire from the board and measuring the wire to ground voltage, you should actually get 12 volts or whatever your battery voltage
is because the wire will still be connected to the battery positive through the relay coil. The voltage should still ALL be there until you ground the
wire to trigger the relay.

Measure the resistance to ground on the terminal of the board the wire was connected to if that is where you are disconnecting it. Maybe you are
getting a ground through the "Battery Condition Meter" if your system has that. My manual's schematic indicates it is optional. Mine has one over that
pantry/vacuum cabinet but IIRC it is not functional unless I turn the system monitor on.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
Thanks. This gives me something to go off of. We did order a solenoid and a couple other parts, so this will be later in the week.

The one I am working on does not start, and it is intermintant. Used to be all the time, but now it sticks 1 out of three times.

Trying to get the cranking reliable then on to checking other things for a good start/run. Starter bracket looks good, i think it is the switches
or k1 sticking.
--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Ken,

I'm sure glad you mentioned my Onan wiring diagram. As you may recall,
Gene Fisher pointed out a while back that I had an error in the area of the
"engine running" circuit. When I looked at it at first, it seemed to be
merely a matter of inaccurately labelled ground. Recently, I studied the
diagram more carefully and found that I made a LOT of errors in my
re-drawing. I think none of them seriously affected anything anyone's
likely to be interested in, but it was/is definitely WRONG. I've been
through and tried to correct all the errors I found. Here's the link to
the new version:
https://drive.google.com/file/d/0B3XquSIYjDleMEVlVUhKeDVpU0k/
view?usp=sharing

I hope someone will compare this version to Onan's original. Apparently no
one had done so during all the years my original has been circulating.

I'll try to replace the version on GMCMHPhotos with this new version. If
anyone finds the old one anywhere else, please replace it with this
corrected on, labelled "KH Onan Wiring 170604".

My apologies for publishing erroneous information.

Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, etc., etc., etc.
www.gmcwipersetc.com

> I am sitting here looking at the Onan Wiring diagram that Colonel Ken
> made. +12 volts should always be on one side of the coil. The Onan board
> controls the K1 coil by applying ground (-12vdc) on the opposite side of
> the coil. There is one wire from the K1 coil to pin 7 on the Onan board.
> There should be no other wiring connections to either the coil terminal or
> pin 7 on the Onan board.
>
> That said, Pin 7 on the Onan board goes only to the N/C point of K2 and no
> where else. So when K2 is powered by the 33VAC from the alternator, the
> K2 N/C point should open up and block any path to the ground side of K1.
> So at this point I would suggest that you have a wiring error, or a short on
> the board, or a tacked relay point on K2. Even if you had a tacked relay
> point, the voltage should drop to K1 when you remove your finger from both
> of the starting switches.
>
> I guess that there is a possibility that there could be a worn spot on the
> coil that when energized the armature might short to. I have never seen
> this but it is the only idea that I have right now on what could be
> causing this problem. That is just a wild guess because I have never seen
> of or
> heard of this failure.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
First, Please use Colonel Ken's wiring diagram. It is a lot easier to read and it gives us a common diagram to talk about.

I was misunderstood where you were taking voltage readings. Just to make sure, I now think you are taking voltage reading at the N/O point on K1 that
goes to the starter and choke. You are not reading the K1 coil leads going to +12 and the K1 coil lead going to Onan board pin 7.

If the above is true, then I need to rethink the problem again.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Mr. Henderson,
I believe your original schematic was correct, with respect to Pin 8.
When I look at PIN 8 on my Onan board, it does not connect to GND.
That's the 30V generator output being rectified by CR1 and filtered by R1 C1.

Regards,
Bill

--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
 
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