Onan Problem

O

omoore

New member
Mar 21, 2018
20
0
0
New Bern, NC
My Onan was wo/rking perfectly when I shut it down. Started it up several
days later and it was only charging 6 volts. By manually pushing the
throttle to increase RPM it went up to 9 volts. I have had old Onans in
boats with the same problem so I sent voltage regulator board out for
inspection. Came back OK. Next I went to the large Onan dealer in town
that charges $125/hour. Three hours later I was told that either the stator
or rotor had shorted out. I was told the repair would be expensive and as
the unit was old it wasn't worth fixing.
I am having a hard time believing that diagnosis. I can't get anyone to
take a look at it--too old. But there must be other things that could
cause the charging problem like those round capacitors?? (I know nothing
about electronics) next to the board.
If anyone has a clue please share it. I really don't want--or have-- to
spend the money to replace this genset.
Thanks
Oliver
1973 Kingsley
Patterson Engine
Alcoa Wheels
 
> My Onan was wo/rking perfectly when I shut it down. Started it up several days later and it was only charging 6 volts. By manually pushing the
> throttle to increase RPM it went up to 9 volts. I have had old Onans in boats with the same problem so I sent voltage regulator board out for
> inspection. Came back OK. Next I went to the large Onan dealer in town that charges $125/hour. Three hours later I was told that either the stator
> or rotor had shorted out. I was told the repair would be expensive and as the unit was old it wasn't worth fixing.
> I am having a hard time believing that diagnosis. I can't get anyone to take a look at it--too old. But there must be other things that could
> cause the charging problem like those round capacitors?? (I know nothing about electronics) next to the board.
> If anyone has a clue please share it. I really don't want--or have-- to spend the money to replace this genset.
> Thanks
> Oliver
> 1973 Kingsley
> Patterson Engine
> Alcoa Wheels

Oliver,

Unfortunately, I have no idea where you are. We do have a GMC guy that can fix it, but he is in Hamilton OH (a little north of Dayton).
At the very least, Jim Miller can give you a definitive answer as to what its problem is even if a field needs rewinding, he can do it. It isn't
cheap, but it is less expensive than any replacement.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Oliver,

I've never had one fail, but your symptoms sound to me like the bridge
rectifier has failed.

Regardless, what you need to do is download and read:
http://gmcws.org/Tech/dsimmons/onan_demo/ . That will probably lead you
directly to the problem.

REMEMBER: Before you remove the bridge rectifier, MARK each of the 4
wires! Two of those 4 wires MUST connect to the correct (+ & -) terminals
on the bridge. The other 2 are interchangeable.

The KBPC5010 bridge rectifier readily available from eBay, etc., is a
suitable, economical, replacement, but you must modify the OEM connector
because of the different orientation of its terminals.

Ken H.

On Tue, Aug 18, 2020 at 1:35 PM Oliver Moore via Gmclist <

> My Onan was wo/rking perfectly when I shut it down. Started it up several
> days later and it was only charging 6 volts. By manually pushing the
> throttle to increase RPM it went up to 9 volts. I have had old Onans in
> boats with the same problem so I sent voltage regulator board out for
> inspection. Came back OK. Next I went to the large Onan dealer in town
> that charges $125/hour. Three hours later I was told that either the stator
> or rotor had shorted out. I was told the repair would be expensive and as
> the unit was old it wasn't worth fixing.
> I am having a hard time believing that diagnosis. I can't get anyone to
> take a look at it--too old. But there must be other things that could
> cause the charging problem like those round capacitors?? (I know nothing
> about electronics) next to the board.
> If anyone has a clue please share it. I really don't want--or have-- to
> spend the money to replace this genset.
> Thanks
> Oliver
> 1973 Kingsley
> Patterson Engine
> Alcoa Wheels
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
Oliver,

I should have mentioned in my earlier note: If you had the roof air
conditioner running when you shut down the Onan, that is probably what
"killed" the bridge rectifier. That action is a strong "No-No!".

Ken H.

On Tue, Aug 18, 2020 at 1:35 PM Oliver Moore via Gmclist <

> My Onan was wo/rking perfectly when I shut it down. Started it up several
> days later and it was only charging 6 volts. By manually pushing the
> throttle to increase RPM it went up to 9 volts. I have had old Onans in
> boats with the same problem so I sent voltage regulator board out for
> inspection. Came back OK. Next I went to the large Onan dealer in town
> that charges $125/hour. Three hours later I was told that either the stator
> or rotor had shorted out. I was told the repair would be expensive and as
> the unit was old it wasn't worth fixing.
> I am having a hard time believing that diagnosis. I can't get anyone to
> take a look at it--too old. But there must be other things that could
> cause the charging problem like those round capacitors?? (I know nothing
> about electronics) next to the board.
> If anyone has a clue please share it. I really don't want--or have-- to
> spend the money to replace this genset.
> Thanks
> Oliver
> 1973 Kingsley
> Patterson Engine
> Alcoa Wheels
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
WE can send over how to replace the Bridge Rectifier.
New rectifiers require the socket to be modified.

On Tue, Aug 18, 2020 at 11:38 AM Ken Henderson via Gmclist <

> Oliver,
>
> I should have mentioned in my earlier note: If you had the roof air
> conditioner running when you shut down the Onan, that is probably what
> "killed" the bridge rectifier. That action is a strong "No-No!".
>
> Ken H.
>
>
> On Tue, Aug 18, 2020 at 1:35 PM Oliver Moore via Gmclist <

>
> > My Onan was wo/rking perfectly when I shut it down. Started it up several
> > days later and it was only charging 6 volts. By manually pushing the
> > throttle to increase RPM it went up to 9 volts. I have had old Onans in
> > boats with the same problem so I sent voltage regulator board out for
> > inspection. Came back OK. Next I went to the large Onan dealer in town
> > that charges $125/hour. Three hours later I was told that either the
> stator
> > or rotor had shorted out. I was told the repair would be expensive and as
> > the unit was old it wasn't worth fixing.
> > I am having a hard time believing that diagnosis. I can't get anyone
> to
> > take a look at it--too old. But there must be other things that could
> > cause the charging problem like those round capacitors?? (I know nothing
> > about electronics) next to the board.
> > If anyone has a clue please share it. I really don't want--or have--
> to
> > spend the money to replace this genset.
> > Thanks
> > Oliver
> > 1973 Kingsley
> > Patterson Engine
> > Alcoa Wheels
> > _______________________________________________
> > 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
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
That is exactly what I was thinking. I have replaced a couple of them for other people. Mine also has never failed. They are very cheap for a
higher rated one at a local electronics store. Or with installation instructions from Jim K at Applied GMC. It should take you less than 1/2 hour
to do it yourself.

> Oliver,
>
> I've never had one fail, but your symptoms sound to me like the bridge
> rectifier has failed.
>
> Regardless, what you need to do is download and read:
> http://gmcws.org/Tech/dsimmons/onan_demo/ . That will probably lead you
> directly to the problem.
>
> REMEMBER: Before you remove the bridge rectifier, MARK each of the 4
> wires! Two of those 4 wires MUST connect to the correct (+ & -) terminals
> on the bridge. The other 2 are interchangeable.
>
> The KBPC5010 bridge rectifier readily available from eBay, etc., is a
> suitable, economical, replacement, but you must modify the OEM connector
> because of the different orientation of its terminals.
>
> Ken H.
>
>
> On Tue, Aug 18, 2020 at 1:35 PM Oliver Moore via Gmclist <

>
> > My Onan was wo/rking perfectly when I shut it down. Started it up several
> > days later and it was only charging 6 volts. By manually pushing the
> > throttle to increase RPM it went up to 9 volts. I have had old Onans in
> > boats with the same problem so I sent voltage regulator board out for
> > inspection. Came back OK. Next I went to the large Onan dealer in town
> > that charges $125/hour. Three hours later I was told that either the stator
> > or rotor had shorted out. I was told the repair would be expensive and as
> > the unit was old it wasn't worth fixing.
> > I am having a hard time believing that diagnosis. I can't get anyone to
> > take a look at it--too old. But there must be other things that could
> > cause the charging problem like those round capacitors?? (I know nothing
> > about electronics) next to the board.
> > If anyone has a clue please share it. I really don't want--or have-- to
> > spend the money to replace this genset.
> > Thanks
> > Oliver
> > 1973 Kingsley
> > Patterson Engine
> > Alcoa Wheels
> > _______________________________________________
> > 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 Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Oliver,
There is some really good information about troubleshooting the Onan on this video.

https://youtu.be/tJcwLyrHMq4

Russell
--
Russell Keith,
1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
Onan, Dunedin, Florida
 
That was one great training tape.

On Thu, Aug 20, 2020 at 9:04 AM Russell Keith via Gmclist <

> Oliver,
> There is some really good information about troubleshooting the Onan on
> this video.
>
> https://youtu.be/tJcwLyrHMq4
>
> Russell
> --
> Russell Keith,
> 1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock
> Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
> Onan, Dunedin, Florida
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
I have that video on my hard drive if any one wants it. Unfortunately it is 99.8 meg and will not go as an email attachment. Also I will not have
email access for the next week.

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