I have a 2014 coachmen Leprechaun Class C with a 4000 Onan, in fact I have 3 because I own a small RV Rental business. A customer returned one yesterday and told me that they tried to use the microwave and the gen shut off (no breakers kicked, the gen physically shut off). I tried this morning, and the micro shut the gen off in the first 5 seconds. I then ran the A/C and everything else for a bit, and tried to run the micro again and it ran for a bit, then shut the gen off again. I tried again, it worked for a minute. The microwave etc worked fine on shore power.I then took the exact same micro out of another of the exact same RV's, and put the micro from the RV that was shutting down the gen into another RV, exactly the same. I basically swapped microwaves between RV's, which the RV's and microwaves are exactly the same. The RV that was good to go ran fine with the Microwave out of the RV that had the gen shutting down, but the RV that had the Gen shutting down fried the microwave from the good RV. So it's definitely not the microwave. The Onan code that I pulled from the troubleshooting guide and the indicator light was 12, which says to contact authorized onan dealer…Any advice or recommendations on what I can troubleshoot? perhaps the outlet that the microwave is plugged into? I'm not sure what to check here, my guess is that there is too much amps or volts getting pushed through the outlet to fry the microwave, but why on earth would is the generator shutting off? there is a 20 amp breaker on going from the fuse box to the microwave, and a 30 amp breaker on the generator and Main breaker inside the RV. What would cause an appliance to shut the generator down vice kicking the breaker?

sounds like an Over voltage problem on ONE leg of the Onan outputthis could be caused by a bad connection on the Other winding..the one with the voltage regulator sense circuit (field current)

Overvoltage condition..........no breaker tripping cause amperage was OKNeed to look up specific model service manual to find procedure to adjust regulator/governor speed/voltage control.Luckily just microwave.....could have fried AC Unit motor or DC control boards, depending on how high voltage went.

Just an educated guess. The microwave is an "unfriendly" load for the generator, with its current draw not directly following the voltage waveform. The circuit breaker reacts to time-averaged current, while there might in reality be very short current spikes many times the breaker value that don't result in a trip. There could be a weak link anywhere in the generator circuitry that can't handle the short current spikes, followed by a protection mechanism detecting it and shutting the generator down. Could also be a problem with the voltage regulator being confused by the unfriendly load, too. Not knowing the Onan internals in any detail, I'd have to say the problem could be with almost anything in the generator part. My first shot in the dark would be to make sure all the electrical connections are tight, clean all of the connectors, and reseat plug-in circuit boards if there are any.

Thanks for the information. I just talked with a gen mech company and they charge $250 to come out. I tested the volts in the outlet that the microwave was plugged into and it reads 119. Let me start by saying again, thank you very much for any and all information/recommendations, by no means am I challenging any input by anyone, I'm extremely grateful for everyones input, but I do want to try to understand as much about the issue as possible because I have very little time to figure it out and get it corrected. An over voltage condition seems to explain why the microwave was fried, but why was the generator shutting off when I would turn on the microwave? and the microwave was plugged up with power to it with no problems with the gen running for hours, only when you operated the microwave would there be any issue. If the outlet was getting too much voltage, wouldn't it fry the microwave even if were on in operation but simply plugged in?

Generator fried microwave after gen shut down several times

18 Replies

TEXAS
Explorer
Nov 29, 2014
Onan has only a one year warranty. I believe you can buy extended warranty. Warranty goes into effect the day the RV is put into service. Not how long it sat on the lot. But if the generator checks out ok. They will expect you to pay the labor.
HTElectrical
Explorer
Nov 29, 2014
I believe the Onan has more than a 1 year warranty though. Not 100% sure on that though.
Snowman9000
Explorer
Nov 28, 2014
HTElectrical wrote:
If it is a 2014 model, why don't you have it repaired under warranty? I am sure the gen is covered?????

That was my thought too, but a 2014 could be out of warranty already. They start coming out in the middle of the year before, if not earlier.
HTElectrical
Explorer
Nov 28, 2014
If it is a 2014 model, why don't you have it repaired under warranty? I am sure the gen is covered?????
Joe417
Explorer
Nov 26, 2014
I don't think I would worry about the Microwave if it's working again. Remember that it has a Microprocessor.

Speculation:: For safety issues, the processor could be monitoring a particular component for temperature. It could hold the processor in reset until it cooled. Specifically the magnetron.(tube)

I'd worry more about the Gen.

There were some posts on here not too long ago, don't remember the specifics, where the Gen was acting erratically.

OP included some pictures where the junction box in the Gen compartment had toasted the wire nutted connections.

Would be simple and couldn't hurt to check. Just turn all AC power off first.
rforehand
Explorer
Nov 25, 2014
Pirate wrote:
This is exactly why I wired my PD surge after the generator. I had a board go out on one generator, it upped the voltage to 160 and fried my microwave.

Pirate, just curious but was the spike a single spike in voltage that occurred and fried the micro? In my case, the gen began shutting off when you'd try to use the microwave, then when I was troubleshooting the problem I had the micro set for 5 mins and when I came back to check on it my microwave was dead, no lights on the microwave worked or anything, so I assumed it was fried. I plugged in another microwave to the same outlet and it worked, so I brought the Microwave in my garbage about 2 hrs later, plugged it up and its working again.
rforehand
Explorer
Nov 25, 2014
Thanks John Wayne. based on your post, it's definitely a gen problem. I'm still confused though as to how the microwave was dead, I even plugged it into two separate outlets, then plugged another microwave into the same outlet to verify power, then tested the outlet with a volt meter and pulled 119v, so I know the outlet had power, but the microwave was dead, no lights on the screen/panel or nothing, then I plugged it into my garage about 2 hrs later and it came on and works like a charm.
John_Wayne
Explorer II
Nov 25, 2014
I'd say if it runs on post power, but does not run on generator power it's a generator problem. Take the microwave in the house and plug it in. does it work?? if so not a microwave problem.
rforehand
Explorer
Nov 24, 2014
Thanks all. I checked out the service manual, it's way beyond my level. I'm going to have someone come have a look. I'll send an update when they get it figured out so others may benefit from the info in the event that they experience something similar.
Pirate1
Explorer
Nov 24, 2014
This is exactly why I wired my PD surge after the generator. I had a board go out on one generator, it upped the voltage to 160 and fried my microwave.