Onan Generator Voltage & Control Issues

Steve Sullivan · 04-21-2016, 12:36 PM

Hoping one of you generator techs can give me some guidance on straightening out my Genset Emerald Plus 4000W Gas unit. It has 2,809 hours on it. I have done the proper maintenance on it since I got it new with my RV in 1996. Have had issues in the past and pretty much got them taken care of. But now it is really driving me bat****.

It started last year with a loss of output power with the Genset running. Never quite able to pinpoint why and swapping out control boards to a proven one had no effect.
Took unit out and gave to local friend who was once a Onan tech. When he fired it up it had output on the stand! He checked what he could check and found nothing wrong with the unit. Put it back in chassis fired up unit and re calibrated output parameters using digital meter. Ran fine and ran various appliances and different load levels. Had previously checked and cleaned brush rings on commutator. No problems while doing all this at the house. Then it did it again Engine running, no output to coach. When I was checking things I looked in the junction box where the generator output wires are wire nutted to the coach conduit. The black wire nut was melted! Thought that connection had loosened and there was arcing in it overheating the plastic. Put things back together and clicked breakers on & off a couple time. Again had power. Did calibration procedure as I have before, ran different appliances and different load levels, all was well. Went to Columbus for a race (about a 2 hr trip). When I fired up the generator for the first time it started and I THINK it had been connected to the coach by the transfer switch with only the reefer unit running. It suddenly began a severe lugging like a huge load had been put on it and it stalled. Post mortem I found the voltage regulator had failed. Checked junction box connections (no issues), all connections on transfer switch, and any wires I could see for damage. Fired it up and it runs but I have not reconnected it to the junction box as of yet. Really don't want to blow another voltage regulator.

I plug RV into outlet on my shop wall via the shore plug when parked. No issues except once when the ground on the plug adapter went south and I got a "slight correction" when I touched the undercarriage changing oil.

HELP!!!

Rich Biebel · 04-21-2016, 08:17 PM

Quote:

Originally Posted by Steve Sullivan

Hoping one of you generator techs can give me some guidance on straightening out my Genset Emerald Plus 4000W Gas unit. It has 2,809 hours on it. I have done the proper maintenance on it since I got it new with my RV in 1996. Have had issues in the past and pretty much got them taken care of. But now it is really driving me bat****.

It started last year with a loss of output power with the Genset running. Never quite able to pinpoint why and swapping out control boards to a proven one had no effect.
Took unit out and gave to local friend who was once a Onan tech. When he fired it up it had output on the stand! He checked what he could check and found nothing wrong with the unit. Put it back in chassis fired up unit and re calibrated output parameters using digital meter. Ran fine and ran various appliances and different load levels. Had previously checked and cleaned brush rings on commutator. No problems while doing all this at the house. Then it did it again Engine running, no output to coach. When I was checking things I looked in the junction box where the generator output wires are wire nutted to the coach conduit. The black wire nut was melted! Thought that connection had loosened and there was arcing in it overheating the plastic. Put things back together and clicked breakers on & off a couple time. Again had power. Did calibration procedure as I have before, ran different appliances and different load levels, all was well. Went to Columbus for a race (about a 2 hr trip). When I fired up the generator for the first time it started and I THINK it had been connected to the coach by the transfer switch with only the reefer unit running. It suddenly began a severe lugging like a huge load had been put on it and it stalled. Post mortem I found the voltage regulator had failed. Checked junction box connections (no issues), all connections on transfer switch, and any wires I could see for damage. Fired it up and it runs but I have not reconnected it to the junction box as of yet. Really don't want to blow another voltage regulator.

I plug RV into outlet on my shop wall via the shore plug when parked. No issues except once when the ground on the plug adapter went south and I got a "slight correction" when I touched the undercarriage changing oil.

HELP!!!

Voltage regulators do fail and can fail in a way you describe. You may also have a stator winding failing. The machine is 20 years old. Those stator windings deteriorate with time. Nothing you can do to prevent a failure. Replace the regulator and it may be the only problem. Lower cost regulators are available from sources other than Onan. Flight systems, Parts for Techs also know as A.S.A.P. sells them. I just repaired a 1999 NHM with a bad V/R and bought a replacement from Flight along with a control board. I have repaired Onan's for 20+ years. Nothing on the output side of the generator other than back feeding it from another power source can hurt the generator. Transfer switches don't allow that to happen unless it was totally burnt up or had welded contacts which just does not happen from my experience. The generators breakers protect it from a dead short on the output side or an overload.

Steve Sullivan · 04-21-2016, 11:19 PM

Thanks Rich! I was hoping you would see my post and respond. I have used Flight Systems and ASAP in the past for parts. Have had a control board go south and also smoked a regulator once. They definitely are an economical alternative to getting bent over by Cummins/Onan. Bought a carb rebuild kit a couple years ago for it and about threw up when I saw what I got for the $$ spent. At least I was able to get the carb back in good shape. Guess I'll hook everything up and run it through it's paces again. When I get to the track I guess I'll make the sign of the cross before I fire it up. LOL
Thanks again!

04-21-2016, 12:36 PM	#1
Steve Sullivan Junior Member Join Date: Nov 2003 Location: West Chester Posts: 64 Likes: 24 Liked 23 Times in 12 Posts	Onan Generator Voltage & Control Issues Hoping one of you generator techs can give me some guidance on straightening out my Genset Emerald Plus 4000W Gas unit. It has 2,809 hours on it. I have done the proper maintenance on it since I got it new with my RV in 1996. Have had issues in the past and pretty much got them taken care of. But now it is really driving me bat****. It started last year with a loss of output power with the Genset running. Never quite able to pinpoint why and swapping out control boards to a proven one had no effect. Took unit out and gave to local friend who was once a Onan tech. When he fired it up it had output on the stand! He checked what he could check and found nothing wrong with the unit. Put it back in chassis fired up unit and re calibrated output parameters using digital meter. Ran fine and ran various appliances and different load levels. Had previously checked and cleaned brush rings on commutator. No problems while doing all this at the house. Then it did it again Engine running, no output to coach. When I was checking things I looked in the junction box where the generator output wires are wire nutted to the coach conduit. The black wire nut was melted! Thought that connection had loosened and there was arcing in it overheating the plastic. Put things back together and clicked breakers on & off a couple time. Again had power. Did calibration procedure as I have before, ran different appliances and different load levels, all was well. Went to Columbus for a race (about a 2 hr trip). When I fired up the generator for the first time it started and I THINK it had been connected to the coach by the transfer switch with only the reefer unit running. It suddenly began a severe lugging like a huge load had been put on it and it stalled. Post mortem I found the voltage regulator had failed. Checked junction box connections (no issues), all connections on transfer switch, and any wires I could see for damage. Fired it up and it runs but I have not reconnected it to the junction box as of yet. Really don't want to blow another voltage regulator. I plug RV into outlet on my shop wall via the shore plug when parked. No issues except once when the ground on the plug adapter went south and I got a "slight correction" when I touched the undercarriage changing oil. HELP!!!

04-21-2016, 11:19 PM	#3
Steve Sullivan Junior Member Join Date: Nov 2003 Location: West Chester Posts: 64 Likes: 24 Liked 23 Times in 12 Posts	Re: Onan Generator Voltage & Control Issues Thanks Rich! I was hoping you would see my post and respond. I have used Flight Systems and ASAP in the past for parts. Have had a control board go south and also smoked a regulator once. They definitely are an economical alternative to getting bent over by Cummins/Onan. Bought a carb rebuild kit a couple years ago for it and about threw up when I saw what I got for the $$ spent. At least I was able to get the carb back in good shape. Guess I'll hook everything up and run it through it's paces again. When I get to the track I guess I'll make the sign of the cross before I fire it up. LOL Thanks again!