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Inverter overvoltage fault when running A/C from generator

Yahoo Message Number: 64001
When running the rear A/C unit in our 2003 Magna Resort 42', the generator will often turn off after a period of time, usually between one and two hours, and the status board indicates the fault "Inverter overvoltage". This never happens with the front A/C unit under any circumstances, and the rear unit operates with no problems when we are hooked up to shore power.
I could understand it when I tried to operate the A/C unit soon after running the slides in or out, as the charger is bulk charging the house batteries, and somehow that overloads the inverter, even though I have it turned off, but the same thing happens when I haven't used the slides and the house batteries are fully charged.
I have had no success trying to get information from Xantrex, and I recently had all the cheap fuel hoses from both the generator and the Hurricane unit replaced with high-quality ones which have no cracks and are not sucking air.
I can usually figure out my own problems, but this one has me stumped. Any advice would be appreciated.

David Jarrett

2003 Magna Resort #6240

Re: Inverter overvoltage fault when running A/C from generator

Reply #1 –
Yahoo Message Number: 64009
David,

Since no one has jumped in, this is what I understand:

Only have problems on rear A/C only when gen is running. Does it with inverter off. This would tell me it is not an inverter issue, the system just thinks it is. Takes time to show up. Time indicates possible heat issue. Is it the A/C itself? Works o.k. on shore, probably not the A/C. Can it be resistance somewhere that generates heat and more resistance over time until it trips the system. I would check the rear A/C 110 circuit breaker for heat when the system trips. I would watch the voltage meters in the coach every little bit and try to catch what is happening. Especially at the 2 hr. mark. Is it a possible problem with the transfer switch. Could be a weak coil that lets go throwing an imbalance. The transfer coils only are pulled in with the gen., shore power they are not used. How to test? Have ready access to the transfer switch and when the fault occurs, check for smell and heat in coils. Be sure all power is off.

Think the top suspect might be the transfer switch until can prove it is o.k.

This is a brain storming session on this issue with what I understand. Maybe it will trip other minds to jump in as well.

Leonard Kerns
97' Magna 5418

Are you sure the gen itself is not having overheating issues, electrical, not water temp. Is it an Onan that has history of slip ring, brush or regulator problems?

Good luck.

Re: Inverter overvoltage fault when running A/C from generator

Reply #2 –
Yahoo Message Number: 64025
David,

You need to pull the blink codes from your generator right after this occurs. Look in your owners manual for the generator and it will tell you how. Then you should know why the gen is shutting down. If that is the "status board" you are talking about, it is referring to the inverter overvoltage in your generator, not the coach inverter. Why that would be happening, I do not know. If you are referring to Xantrex inverter, I do not believe that would cause your generator to shut down, but if the gen is putting out too much voltage, it could cause your inverter to shut down. You could have two separate problems.

Rich 2002 Magna

I could be wrong, but I do not believe that the inverter would cause your generator to shut down.

Re: Inverter overvoltage fault when running A/C from generator

Reply #3 –
Yahoo Message Number: 64030
Since we are brainstorming, We need to Know what generator David has. If it's a 12.5kw Onan what is the coolant temp when it shuts down? I've seen "Feedback circuits" miswired on many different types of equipment so I wouldn't rely on the error message as if it was the gospel. I agree with turning off the inverter and trying it. Watch and verify what the gauges are doing while you try it with the inverter off. Watch the volts the Generator is outputting. A/C units can draw different amps depending on many variables (like the refrigerant charge for starters). The rear unit may draw more amps than the front causing the generator to work harder with the back unit. Try the front unit and add a amp draw of a noticeable amount from something else and see what happens.
My Generator was shutting down after about an hour or two when I would run all three A/C's. I've got my Onan 12.5kw Generator out of the coach right now but the fan belt was loose and worn. Put a new fan belt on, changed coolant to Rotella ELC, oil and filter, fuel filter, air filter. There was a coolant line nearly pinched in half by the enclosure which I moved. Found a petrified mouse wedged in the air filter canister housing. Put a new exhaust pipe on as someone had bent the original and restricted about half of it's flow capacity. I Started the generator out of the coach and it is much quieter. Hope this cures my problems.
I would load up the generator with a pretty good load on it without the rear air and see if I could get the Genset to shutdown.
Kevin Burns

00 Affinity 5865

Re: Inverter overvoltage fault when running A/C from generator

Reply #4 –
Yahoo Message Number: 64032
Just for the record. Is Inverter Overvoltage referring to the genertor's built-in inverter, or the coach inverter (which should have nothing to do with this issue)?

Herb

Former owner of 2007 Allure 430 #31466 whose generator had an inverter control board issue

Re: Inverter overvoltage fault when running A/C from generator

Reply #5 –
Yahoo Message Number: 64087
I worked all day yesterday diagnosing this problem. I discovered several things:
1) There is no inverter built into the genset itself. There is a controller, which is essentially a voltage regulator, built into it somewhere. It is probably nothing more than a plug--in modular circuit board which is beginning to fail when the generator is forced to supply a heavy current. If you look on eBay, you can find several of these with different part numbers, from the old, outmoded types for $30-$40 to the newest ones for $400-$600.
2) Onan obviously doesn't want the owner of the unit to find this piece of equipment. Their dealers must have lobbied very hard to get the company to put it in a place where the typical motor home owner would not be able to repair it without taking it into one of their facilities. I began taking the generator housing (box) apart, thinking I would find the module in due time. However, I got to the point at which I would either have to take the whole thing apart, which would have involved more time than I have right now, or give up on it. As the problem does not occur with just a moderate load, I decided to give up, as most of time we use shore power in RV parks, and we have an extremely important medically-oriented trip to Phoenix scheduled for this coming Friday. I did not want to get to the point where I had done something irreversibly wrong that could result in our not being able to leave as scheduled.
3) I think this a cheap trick on Onan's part. This module should be placed in a very convenient location so that, should it need replacement, it can be done by the owner himself. I have also noticed, through my Internet searches, of which I have done many, that Onan does not make any diagrams, manuals, etc., available to those of us who want to see the workings of their products. This is in clear contrast to a company like HWH, which readily makes such information available.

I thank those of you who tried to help me with this problem. I hope what I have written here will shed some light on it so that others who have the same one can save themselves some trouble.

DRJ

Re: Inverter overvoltage fault when running A/C from generator

Reply #6 –
Yahoo Message Number: 64097
I don't know what generator you have but my Onan 12.5kw has a circuit board in the resonator. It is attached to the front panel of the Generator so you have to take it off. There are about 8 nuts holding it on. If you follow your air filter canister back your clean air intake hose should be connected to it. I guess they put it in there to keep it cool.
Kevin Burns

00 affinity 5865

Re: Inverter overvoltage fault when running A/C from generator

Reply #7 –
Yahoo Message Number: 64098
You are correct. Had our module replaced two years ago. Several hours of labor out and several hours back in. As I recall $1200-1300.
It was a circuit board.
Jw

06 inspire 51544

Re: Inverter overvoltage fault when running A/C from generator

Reply #8 –
Yahoo Message Number: 64114
You have still neglected to inform us what model of generator you have or where this inverter message came from. You seem to have two A/C's from what I can gather. If so, and like my Magna, you probably have an 8kw HDKAK. If so, it definitely has an inverter in it. The rest of what you are raising is beyond my knowledge.

Rich 2002 Magna
 

Re: Inverter overvoltage fault when running A/C from generator

Reply #9 –
Yahoo Message Number: 64118
Keep us posted, Im a Cat retired power systems tech. I have worked on most Onans in my other life, Radio and TV ststions use them in thier field trucks. I went to school and yes its difficult for untrained endusers to repair. Onan had Factory Books for dealers use only. I would always tell my endusers let me repair it as you get a warranty and if I burn something up you dont pay! This is dangerous work and sad to say should be left to the pro's.I suggest to be careful if you attempt repairs on you unit. Ken 99 Allure 30356 with a power tech 7kw. Sone units like the older ones have Brushs that get dirty and yes voltage regulators fail. Please be careful friend.