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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14436
Experience:  Certified on Onan and Generac generators
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I have an Onan 10-HDCAA Spec A generator in my Zephyr.

Customer Question

I have an Onan 10-HDCAA Spec A generator in my Zephyr. Recently the generator would run a few seconds and stop resulting in a 27 error code. I trouble shoot the code per the manual and all results pointed back to the control board. I replaced the control board. Now when i try to start the generator it cranks a half turn or so then stops even though the start switch is held in the start position. I checked K2, the relay that supplies power to the starter solenoid and it is fine. Also, plenty of battery power. I also used the old board and received the same results. I am completely baffled because the engine cranked fine prior to replacing the board. I am not a big believer in coincidence so i feel i may have caused the problem when replacing the control board. I would like to check the starter solenoid but i can't seen to locate it. I can't see the starter either so i am afraid i may have to remove the generator from the RV. Anyone's thoughts would be very much appreciated.
Submitted: 1 month ago.
Category: Small Engine
Expert:  Hank F. replied 1 month ago.

Hello, my name is ***** ***** I am going to assist you with this.

What is the serial number of the genset?

Customer: replied 1 month ago.
Hi hank, s/n f020381463
Expert:  Hank F. replied 1 month ago.

It really does not make any sense that it would only crank 1/2 turn after replacing the controller. That should not have any effect on anything.

The starter is located on the back side of the engine, up high.

You can access it through the top access panel.

The starter is the first place you need to check. It is doubtful that this is something internal, but do not rule it out completely just yet.

You state that you checked K2. Exactly how did you check it? Did you simply pull it out and test to see if it was switching? Or did you actually check to make usre you had good 12V going through it while it was activated?

Customer: replied 1 month ago.
Measured 12 volts. I agree that the control board should have no effect but I thought I might have done something whole removing and replacing the board. So the starter is on the top. I quickly looked there yesterday but figured it wouldn't be on the top. So much for that. Is the starter solenoid there also?
Expert:  Hank F. replied 1 month ago.

Yes, the solenoid is built on to the starter, just like they were on older cars.

Customer: replied 1 month ago.
HI Hank, Let me tell you a little about myself. I have an electrical engineering degree. I have rebuilt and installed 3 auto engines in my lifetime. I am no expert by any means but i do have some experience. I am pretty mechanically inclined. Having said that i am feeling really stupid right now. i cannot locate that starter. I looked high and low. Although my vision is somewhat obscured by the top cover I don't even see any wires going in that general direction. I really don't think it is where the book says. BTW i have the Workshop manual for the engine and the service manual for the generator.
Expert:  Hank F. replied 1 month ago.

The starter is on the back side of the engine, directly opposite the oil filter.

If you were to drill a hole through the oil filter, and through the block, it would hit the starter.

Customer: replied 1 month ago.
ok i am going to have to remove the top cover to see down there. I'll get to it shortly then get back to you. Thanks Hank.
Customer: replied 1 month ago.
wanted to let you know i did not work on the genset yesterday because it rained most of the day. Will try again today.
Expert:  Hank F. replied 1 month ago.


Customer: replied 1 month ago.
Good timing Hank. i am working on the genset right now.
Expert:  Hank F. replied 1 month ago.


Customer: replied 1 month ago.
Hi Hank,
I checked the connections on the starter. All tight and clean. I assume you have the wiring schematic (prior to spec c). I shorted K2-87 and 30 to bypass the relay contact. The starter cranked fine. I reconnected the relay and used the local starter switch and the starter would only crank 1/2 turn or so before stopping. The only thing i see left in the loop is the started switch which i doubt has an issue and the control board pin J1-6 which provides power to the relay k2. What i can't figure out is what de-energizes K2 when the generator starts normally? It can't just be the starter switch can it? I am assuming there is a sensor somewhere that alerts the control board that the engine has started thus de-enerzing K2. am out of ideas. What do you think?
Customer: replied 1 month ago.
oh, one more thing i forgot to tell you. I replaced K2.
Expert:  Hank F. replied 1 month ago.

Yes, I have the schematic. I have been an Onan tech for 15 years.

Starter disconnect occurs when the controller senses that engine speed has reached 800 rpm. It gets speed sensing from the frequency of the AC output.

From what you are describing, you are down to 1 of 2 issues:

1. Bad connection at P1-6.

2. Bad controller.

In 15 years, I have never seen a pin go bad on its own (it's a different story when people go to probing in there with a multimeter), but I have replaced many controllers.

Customer: replied 1 month ago.
The original problem way back was error code 27. So the engine would crank and start but to stop after several seconds due to the PMA SENSE LOST FAULT. When i replaced the board the starter failing to crank problem occurred. If you remember i put the old controller back in and the starter problem still existed. So i tend to think it is not a controller problem. I'll check P1-6 but Is there something else we are missing. Thanks Hank.
Expert:  Hank F. replied 1 month ago.

The power to activate K2 comes directly from the controller.

If you jump 12V to pin 85 of the K2 (pin 30 to 85) this will be the same as the controller powering up K2.

If it still only cranks 1/2 turn, there is a problem somewhere past K2.

If it cranks normally, the problem is before K2.

The only thing before K2 is the controller and the wire between the controller and K2-85.

Since you did replace the controller, it is very possible that you bent/damaged a pin. They are very small, and easily damaged.

Expert:  Hank F. replied 1 month ago.

Did you find anything yet?

Expert:  Hank F. replied 27 days ago.

Was this what you wanted to know?

Customer: replied 25 days ago.
Hi Hank, Sorry had to go out of town for business. Haven't had a chance to get back to the generator. I will do more testing tomorrow. Thanks sir.
Expert:  Hank F. replied 24 days ago.


Customer: replied 24 days ago.
Hi Hank, Been raining here so didn't get any troubleshooting done. Supposed to rain most of the day today. I'll keep you posted.
Expert:  Hank F. replied 23 days ago.