Onan starting

I am in total agreement with Jim's conclusions in the previous posting. I have repaired many of those boards, but I do not do it any more. I got
tired of repairing them only to have a different component or foil pattern fail a few months later.

The most common failure is for the K2 relay coil to open. That relay is no longer available so you have to rig up a different part to replace it. I
have had the C1 go bad, on another board R1 go bad, and also diode CR1 go open.

If you are seeing 27.5 volts AC between pins 5 (or 11) and pin 8, then as Jim says your problem is on the board.

After several repairs to my board I finally bought a dinosaur board and have never had another problem. Jim K. at Applied GMC has them in stock.

For future reference, if you want to test to see if the oil pressure switch is causing a problem, simply disconnect it. If the problem goes away and
the engine stays running, then the problem is the switch (or low oil pressure).

Call Jim K.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Thanks to both Kens for their comments. Let me summarize where I am...
> - Genset wouldn't stay running
> - Jumpered 5 to 9 and it ran fine, mistakenly believed I was only bypassing LOP
> - Replaced LOP switch, problem still exists
> - Tested voltage on pin 11, read 12.5 volts DC, mistakenly believed regulator failed
> - Disconnected as instructed, voltage unchanged
> - Was informed pin 11 voltage was AC, tested again and read 27.2 VAC
> - Understand regulator is unnecessary and unrelated to voltage on pin 11, removed from circuit
> - Will investigate relay on board not pulling in although correct voltage is present by examining board and components in detail and cleaning all
> contacts then retest.
Congratulations. You were able to filter the wheat from the chaff in the responses.

Make sure you have an electrical path from the flywheel alternator to pin 8. Any mention of pin 11 for that voltage is a red herring. When you take
the voltage regulator out of the equation, you still need to get the flywheel voltage to pin 8. That is where the board is looking for the "generator
running" 28VAC signal. Onan put a three-way connector on the regulator to split the flywheel alternator output into two paths, one fed the voltage
regulator and the other fed pin 8.

You are correct that now you need to figure out what component on the board has failed. And I can't help much, since I never had to do that. I HAVE
had to figure out that when a PO disconnected the voltage regulator on mine, he did it wrong and, instead of keeping the three-way connector and
taping it up, he threw away the connector and the wire from the voltage regulator to pin 8 eliminating the path from the voltage regulator to pin 8.
Mine only runs with pin 5 jumpered to pin 9 until I get a path to pin 8 to see if it will run without jumpers. And I need to get a working voltage
regulator or something to keep my dedicated Onan battery charged.

For anyone who stumbles on this thread in the future, when trying to figure out if the 28VAC "generator running" signal is present, just measure pin 8
to ground for AC voltage. Pin 8 is where the board is looking for 28VAC. That's where you should look for it. Measuring 5 to 11, or 11, or whatever,
is measuring it indirectly.
--
73 23' Sequoia 4 Sale
73 23' CanyonLands Parts Unit 4 Sale
Upper Alabama
"Highest price does not guarantee highest quality."
 
Pulled the board this morning before heading out for PT and believe I spotted the problem immediately...broken wire to pin 5 on the top of the board.
Looks like stress and vibration got to it. I'll repair that before going any further.
--
1978 Eleganza II
 
A lack of connection will do it every time.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
If fixing this connection to pin 5 does not fix your problem, be aware that the excellent diagram that Colonel Ken provided you does not show the
voltage regulator and actual the point to point wiring from Pin 5 and pin 8 to the winding of the alternator.

http://www.gmcmhphotos.com/photos/data/5813/KH_Onan_Wiring1.pdf

One of those wires (I believe pin 8) goes through the connection at the regulator. It is the two wires that are connected together and were plugged
on to one tab of the regulator. It can remain disconnected from the regulator but the two wires must remain connected to each other.

You ought to be able to verify the integrity of the circuit between pin 8 and pin 5 through the alternator winding with an ohm meter. It should read
a low resistance of a few ohms.

I hate to say this, but at this point I believe the broken wire at pin 5 that you found was not your original problem. If this wire was broken at the
time that you read the 27.5 volts AC, that reading should have been 0 volts.

I hope that I am wrong and that you have found the problem.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> If fixing this connection to pin 5 does not fix your problem, be aware that the excellent diagram that Colonel Ken provided you does not show the
> voltage regulator and actual the point to point wiring from Pin 5 and pin 8 to the winding of the alternator.
>
> http://www.gmcmhphotos.com/photos/data/5813/KH_Onan_Wiring1.pdf
>
> One of those wires (I believe pin 8) goes through the connection at the regulator. It is the two wires that are connected together and were
> plugged on to one tab of the regulator. It can remain disconnected from the regulator but the two wires must remain connected to each other.
>
> You ought to be able to verify the integrity of the circuit between pin 8 and pin 5 through the alternator winding with an ohm meter. It should
> read a low resistance of a few ohms.
>
> I hate to say this, but at this point I believe the broken wire at pin 5 that you found was not your original problem. If this wire was broken at
> the time that you read the 27.5 volts AC, that reading should have been 0 volts.
>
> I hope that I am wrong and that you have found the problem.

You realize there are two Pin 5 connections on that board. I didn't believe it at first but there are two, this one along the top edge of the board
and then another closer to the bottom.
--
1978 Eleganza II
 
Aren't the 2 pin 5 connectors connected together with a trace on the back of the board?
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.
 
>
> Aren't the 2 pin 5 connectors connected together with a trace on the back of the board?

They are duplicates - placed on the board for wiring convenience - both will be functionally equivalent.

—Jim

Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
 
> Yes, they are common on the board and both have a wired connection.

Yes, they are and I have a board that confounded me for a while because the trace to one of the #5s had corroded away and I was measuring at the
other.
I think went the copper starts to fall off it is a good time to give up.
**Just another recommendation for thinking about a new control board.**

Does anybody know if the Dinosaur Board is a modern duplicate (same schematic and values) or a re-engineer of the Onan board.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
The dino board is a redesign using modern components. My experience with the originals is, 'shotgun' the caps and diode and repair burnt/corroded
runs and poor wire connections and unless there;s a dead relay they work. The relays are replaceable, K2 requires a pair glued together. I do them
on an 'if as and when' basis, and tell people if they're in a hurry get a new board, either dino or oem from JimK. I currently have a half dozen
waiting on me, all but one spares from Billy and that one from a GMCer who has a borrowed dino board running his Onan. Given the vagaries of my
life, it's going to be a bit yet before they're healed. (Transmission replacement, buying the child a house, dog shows, flu hers and mine, etc.)

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
> The dino board is a redesign using modern components. My experience with the originals is, 'shotgun' the caps and diode and repair
> burnt/corroded runs and poor wire connections and unless there;s a dead relay they work. The relays are replaceable, K2 requires a pair glued
> together. I do them on an 'if as and when' basis, and tell people if they're in a hurry get a new board, either dino or oem from JimK. I currently
> have a half dozen waiting on me, all but one spares from Billy and that one from a GMCer who has a borrowed dino board running his Onan. Given the
> vagaries of my life, it's going to be a bit yet before they're healed. (Transmission replacement, buying the child a house, dog shows, flu hers and
> mine, etc.)
>
> --johnny

Johnny,

Thanks, That is most of what I really needed to know.
I still haven't finished my "Onan simulator" because until this last I was able to patch and go.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
> If fixing this connection to pin 5 does not fix your problem, be aware that the excellent diagram that Colonel Ken provided you does not show the
> voltage regulator and actual the point to point wiring from Pin 5 and pin 8 to the winding of the alternator.
>
> http://www.gmcmhphotos.com/photos/data/5813/KH_Onan_Wiring1.pdf
>
> One of those wires (I believe pin 8) goes through the connection at the regulator. It is the two wires that are connected together and were
> plugged on to one tab of the regulator. It can remain disconnected from the regulator but the two wires must remain connected to each other.
>
> You ought to be able to verify the integrity of the circuit between pin 8 and pin 5 through the alternator winding with an ohm meter. It should
> read a low resistance of a few ohms.
>
> I hate to say this, but at this point I believe the broken wire at pin 5 that you found was not your original problem. If this wire was broken at
> the time that you read the 27.5 volts AC, that reading should have been 0 volts.
>
> I hope that I am wrong and that you have found the problem.

I had another look at the schematic and see your point, it's doubtful the broken connection is my problem. I've gone over the board closely, repaired
the broken connection, cleaned and reseated the others with dilectric grease and I have tested the continuity of the coils for both relays and they
appear to be fine. I'll reinstall it and see what happens.

--
1978 Eleganza II
 
> > If fixing this connection to pin 5 does not fix your problem, be aware that the excellent diagram that Colonel Ken provided you does not show
> > the voltage regulator and actual the point to point wiring from Pin 5 and pin 8 to the winding of the alternator.
> >
> > http://www.gmcmhphotos.com/photos/data/5813/KH_Onan_Wiring1.pdf
> >
> > One of those wires (I believe pin 8) goes through the connection at the regulator. It is the two wires that are connected together and were
> > plugged on to one tab of the regulator. It can remain disconnected from the regulator but the two wires must remain connected to each other.
> >
> > You ought to be able to verify the integrity of the circuit between pin 8 and pin 5 through the alternator winding with an ohm meter. It
> > should read a low resistance of a few ohms.
> >
> > I hate to say this, but at this point I believe the broken wire at pin 5 that you found was not your original problem. If this wire was
> > broken at the time that you read the 27.5 volts AC, that reading should have been 0 volts.
> >
> > I hope that I am wrong and that you have found the problem.
>
> I had another look at the schematic and see your point, it's doubtful the broken connection is my problem. I've gone over the board closely,
> repaired the broken connection, cleaned and reseated the others with dilectric grease and I have tested the continuity of the coils for both relays
> and they appear to be fine. I'll reinstall it and see what happens.


Hey, give it a try and see what happens. You may have fixed it. I have been wrong before.

If you still have it out, put an ohm meter across the relay coil and see if you have a reading. I have seen many of them with open relay coils. I
had one once with the relay cover off that you could see the fine wire on the coil broke where I could get to it. I simply re-soldered the fine wire
back to the terminal connection inside and it has been running for many years since then.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Found the problem...the diode in line from Pin 8 is open. And not just open, but broken in half. I've seen that before with these smaller diodes,
often where there's vibration in addition to heat.

I gave away my bins of various electronic components years ago so will have to wait until tomorrow to find and replace it.

And broken wire at Pin 5 was indeed a red herring. Although there's wire from it to the connector, there's no wire on the mating connector.
--
1978 Eleganza II
 
> Found the problem...the diode in line from Pin 8 is open. And not just open, but broken in half. I've seen that before with these smaller diodes,
> often where there's vibration in addition to heat.


A shorted C1 or K2 will do that too. Capacitors of that age are notorious failure items as I’ve learned firsthand from fixing piles of 1970’s and 80’s vintage HP laboratory equipment over the years.

Unfortunately too many people check go after the control board last instead of first and in the process waste a lot of their time and get really frustrated in the process.

BTW that same CR1/R1/C1/K2 circuit section is where some of the Dino boards have a design problem resulting in smoked R1 and K2 coil winding.

--Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH

“80% of Onan engine problems are control board problems”
 
Ken,
Got to give you credit for your patience.
Since our customer will not tolerate that kind of labor time, we just
replace defective boards.
Same goes for alternator and carburetor.
So many replacement of parts and waste.

On Sun, Jan 22, 2017 at 2:40 PM, Ken Harland
wrote:

> Found the problem...the diode in line from Pin 8 is open. And not just
> open, but broken in half. I've seen that before with these smaller diodes,
> often where there's vibration in addition to heat.
>
> I gave away my bins of various electronic components years ago so will
> have to wait until tomorrow to find and replace it.
>
> And broken wire at Pin 5 was indeed a red herring. Although there's wire
> from it to the connector, there's no wire on the mating connector.
> --
> 1978 Eleganza II
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
The older boards used glass envelope diodes, the newer ones used epoxy diodes. I kus replace all of them, often one or two of the glass ones are
broken. I replace the caps too, they have a kimited lifetime. Fortunately, Onan discontinues these machines before the dreaded 'pregnant capacitor
syndrome' appeared in electronics, though it's a good idea to check your replacements for source and age to make sure they aren't subject...
especially if like me you source them cheeep on ebay. General purpose diodes are less than a nickel each in hundred lots, the caps are sometimes as
much as fifteen cents for the large one. Electrical equivalent relays for K2 aren't cheap, but you can cascade a sensitive relay and a ten amp 12
volt for a couple of dollars max. I epoxy them together and mount them with buss wire.
Note that an average bench tech costs his employer ~~ 32 dollars an hour plus bennies. If they can be kept to 40, then the rule of thumb of 2.5 times
labor invoiced means you'll pay 100 an hour, roughly the going rate around here. You probably aren't going to fix these cards commercially at that
rate. Do it for fun and practice as I do, or buy a replacement.

--johnny
--
'76 23' transmode Norris upfit, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"The road goes on forever, and the party never ends" --Robert Earl Keen
 
Jim Miller, thanks for the heads up on the cap, I'll check it as well.

Jim K, I'm going to order a replacement board as a spare regardless, I have the time to work on such a problem now but won't care to if we're
traveling.

Johnny, I get that completely, not worth it except for one's own sense of accomplishment.
--
1978 Eleganza II
 
It sounds like you have found the problem. Now the question, as Jim Miller has stated, is "what caused it to blow?". Please listen to what Jim
Miller suggested. I have found problems with all of those components on various boards in the past.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
You must log in or register to reply here.
Get your shine on at www.cruzingear.co
GMCMI Fall 2026 Rally

Share this page

Share this page
Top Bottom
Back