Another Onan 4000 ky problem

Rdy1 · 10-15-2017, 07:13 PM

I have a Onan 4000 ky k series. It is in my RV and is 7 years old with very low hours. It runs and starts great but once it runs for about 15 minutes it shuts down and gives a 12 code over voltage. You can start it again with no load and once load is put on it shuts down. You can let it rest for 1/2 to one hour and will do the same sequence. I can start it with no load and put the load on it and I can see it quickly spikes on the volt meter to 157 volts otherwise it will run with 120 to 121 volts. It is not specific appliance. It can be the refrigerator or the air conditioner or even the AC to DC converter. I just don’t want to replace the control module in it if that is not it. I just bought the RV last year.

Rich Biebel · 10-16-2017, 06:56 AM

The control is an all in one PC board. It controls everything and is also the voltage regulator. There really is nothing else that would cause the voltage to max out. Unregulated they will show 150-160 volts. I would test it with no loads applied and use a load bank tester to apply various loads up to the rated max (33 amps) and see what it does. Most motorhomes have a connection box near the generator. Disconnect the generator at that box and tie my loadbank on right there. It would isolate the machine and remove any potential issue in an appliance as the cause for the voltage rise. Load banks are resistive testers. Just like a toaster. Those Controls do go bad and do all sorts of odd things. I have 2 4 KY's myself. Great machines in spite of some issues.

Rdy1 · 10-17-2017, 06:41 AM

Rich,
Thanks for you help. I may have a control board to test it. If not I will would make an appointment with your employer so you could test it. It is the closest place to me and I trust your work.

10-15-2017, 07:13 PM	#1
Rdy1 Junior Member Join Date: Oct 2017 Posts: 2 Likes: 0 Liked 0 Times in 0 Posts	Another Onan 4000 ky problem I have a Onan 4000 ky k series. It is in my RV and is 7 years old with very low hours. It runs and starts great but once it runs for about 15 minutes it shuts down and gives a 12 code over voltage. You can start it again with no load and once load is put on it shuts down. You can let it rest for 1/2 to one hour and will do the same sequence. I can start it with no load and put the load on it and I can see it quickly spikes on the volt meter to 157 volts otherwise it will run with 120 to 121 volts. It is not specific appliance. It can be the refrigerator or the air conditioner or even the AC to DC converter. I just don’t want to replace the control module in it if that is not it. I just bought the RV last year.

10-16-2017, 06:56 AM	#2
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: Another Onan 4000 ky problem The control is an all in one PC board. It controls everything and is also the voltage regulator. There really is nothing else that would cause the voltage to max out. Unregulated they will show 150-160 volts. I would test it with no loads applied and use a load bank tester to apply various loads up to the rated max (33 amps) and see what it does. Most motorhomes have a connection box near the generator. Disconnect the generator at that box and tie my loadbank on right there. It would isolate the machine and remove any potential issue in an appliance as the cause for the voltage rise. Load banks are resistive testers. Just like a toaster. Those Controls do go bad and do all sorts of odd things. I have 2 4 KY's myself. Great machines in spite of some issues. __________________ Rich Biebel S/C 1479 Stock 147R

10-17-2017, 06:41 AM	#3
Rdy1 Junior Member Join Date: Oct 2017 Posts: 2 Likes: 0 Liked 0 Times in 0 Posts	Re: Another Onan 4000 ky problem Rich, Thanks for you help. I may have a control board to test it. If not I will would make an appointment with your employer so you could test it. It is the closest place to me and I trust your work.