Onan 5500 trips top breaker, can't run 110 outlets

Our Onan 5500 gas generator keeps popping the top breaker, also causes inverter to flash and smoke. Inverter is new because we thought that was the problem. Generator has 250 hours. We are using 2 deep cell batteries and a marine battery. We have a Coachman Mirada 340MBS 2003.

Earlier in the season, we were in an electrical storm and the campground lost power. We ran our Onan 5500, and used the AC. We have 1 AC unit.  This last week, we used our generator, had no electrical available at campsite. After a couple of days of using AC, refrigerator, water heater and tv, our generator made a pop, then the inverter started smoking in the coach.

We replaced the inverter, but we still can't get the generator to run without tripping the top breaker. Our new inverter also makes a visible flash of light when the generator breaker trips. We can use our AC and all other stuff when plugged in to an electrical source.

Does anyone out there have any ideas?

Thanks in advance!

Welcome to the forum.
Do you have a INverter or a CONverter?  A INverter converts 12 Volt DC power (from the battery) to 110 Volt AC. A CONverter converts 110 Volt AC (from shore power or generator) to 12 Volt DC.

I had the same question Rene. I think the OP is likely talking his converter, but maybe he can confirm that for us.

For the OP... your converter needs 120 volts A/C to operate. It gets that power from either a shore-power connection, or the generator. The converter then supplies 12 volts to your 12 volt systems (Lights, water pump etc.) It also supplies power to your House battery charger, which is usually part of the converter itself.

When plugged into shore-power, or when running off generator-power, 120 volts A/C is also being supplied to your A/C appliances via circuit breakers (Air conditioner, microwave oven etc.) If you're not experiencing the same problems when running off shore-power, your transfer switch may not be functioning properly. The transfer switch simply switches between A/C power sources and usually prioritizes the generator if both sources are hot.

All Onan gensets I'm familiar with will flash a series of lights (on the Start/Stop switch) if there's a problem with the generator. The number of flashes corresponds to a fault code for troubleshooting. Is the switch flashing?

Kev

Well, the most obvious reason for tripping a breaker is an amp overload. Have you checked for a short in the wiring from genset to transfer switch? Oand the genset side of the auto transfer switch itself?

As for the genset flash codes, there won't be any since the Onan isn't shutting down unexpectedly. It's just a breaker tripping.

There could be some sort of internal fault in the genset, but check the obvious and superficial things first.

Right, the most obvious reason for tripping a breaker is overload. But we don't have a single thing running when it trips.

The spark or flash is not coming from the generator , it's coming from the inverter

Since the OP said everything works when plugged into shore-power, I'd suspect that the transfer switch may not be functioning properly - perhaps not making a solid connection when switched to generator-power. I can't think of another reason that would explain why one A/C source (shore-power) would power everything with no problems, yet the genset won't. I'm also wondering if the genset is flashing any fault codes. He didn't mention any, so I assumed there weren't any. 

And I'm still wondering if the OP is talking about the converter, not the inverter.

Kev

He said that the breaker tripps and the INVERTER flashes and smokes....

I think he had an inverter.. and it's defective. I have seen this happen when a RVer plugged into SHORE power.. The Inverter smoked because the transfer switches did not transfer properly. And I mean SMOKED..  We never did find the failed device ended up installing a manual switch.

Right, the most obvious reason for tripping a breaker is overload. But we don't have a single thing running when it trips.

Click to expand...

That's why I suggested checking the wiring between genset and transfer switch, and the genset relays in the transfer switch itself. That's the only part that is unique to genset vs shore power. A short there will be an instant overload. I would disconnect the genset wires from the transfer switch and see if it still trips, and check the genset output voltage and frequency if it does not. You can check voltage with most any VOM, but only the better ones have frequency (Hz) capability. Most recent model Onans have their own built in frequency check, though, and it would shut itself down if out of range.

As for the converter, any sort of flash there is a bad sign, regardless of the power source. But you say there is no flash there when you plug to shore power?

We will check the wiring. This generator is a replacement for the factory installed gen set that came with the coach.  So it was not wired at the factory. Still it has worked in the past, but just for short periods of time.  Our transfer switch is automatic and built in somewhere. I'll see if I can trace the wiring. Maybe we have a damaged transfer switch wire. And yes, no spark in the inverter when on shore power. Thanks

Nipigon16 said:

We replaced the inverter, but we still can't get the generator to run without tripping the top breaker. Our new inverter also makes a visible flash of light when the generator breaker trips. We can use our AC and all other stuff when plugged in to an electrical source.

Click to expand...

What kind of inverter do you have?  If it has an internal transfer relay the flash may be nothing more than the relay switching from one source of power to another when the generator breaker trips.

While it's not a good idea to switch power sources while under a load, the spark you're seeing may be normal behavior.

Knowing what kind of inverter you have would confirm or rule out this possibility.

Ok, great! We just installed a Parallax SR Series Power Converter/Charger w/Fuse Board 6345RU. It is the replacement for the one that sparked and smoked. My husband installed it. He is pretty handy, but certainly not perfect at all of this RV idiosyncrasies.

Nipigon16 said:

Ok, great! We just installed a Parallax SR Series Power Converter/Charger w/Fuse Board 6345RU. It is the replacement for the one that sparked and smoked. My husband installed it. He is pretty handy, but certainly not perfect at all of this RV idiosyncrasies.

Click to expand...

So it is a CONverter. Thanks.

Could it be a short in the cables running from the converter to the batteries? If it were me, I would shut off the circuit breaker for the converter, and then start the generator.

Paul & Ann said:

Could it be a short in the cables running from the converter to the batteries? If it were me, I would shut off the circuit breaker for the converter, and then start the generator.

Click to expand...

I don't think so Paul. According to the OP, everything works while on shore-power. The only time the CONVERTER sparks is when A/C power is being supplied by the genset, which also trips the genset's 30 amp breaker (Pretty sure it's a 30 amp.) The only component I'm aware of that's in front of the CONVERTER is the transfer switch.

Kev

You are no doubt correct. I am just trying to figure out why the converter is sparking and smoking.

Yes, exactly what is happening Kevin. So the consensus is to check the transfer switch. When we removed the cover to the automatic generator transfer switch, burnt smell was very strong. So our next mission, should we agree to accept it (lol), is to try to replace that transfer switch. Ok hubby is back out there trying to find a way to remove it. Fingers crossed here.

Thanks everyone for your help. We will keep you posted on our search for that transfer switch.

This is our first motorhome. I previously owned travel trailers when I was single. The first was used and a heavy beast. Then I got a new lightweight one that my van could easily pull. Then I upgraded to a 3/4 ton cargo van. Then I upgraded to a bigger lightweight new TT. I sold all of that and was RV free for a couple of years.

Then I was remarried and with my new husband, we decided to buy a used motorhome. We found a 2003 Coachmen Mirada340MBS with only 18,000 miles on it. The generator and awning were new. We remodeled the interior, took a few short trips close to home.

Then last week we took a 1200 mile road trip which included camping without shore power. And that's when the problem with the generator popping the 30 amp breaker started.

We also blew a spark plug on the road and had to be towed. The repair company (Handley Repair, Paducah KY) told us that the Ford Triton V-10's were defective, ( 2002-2013) and that that all of the spark plugs would most likely all blow and strip the threads in the housing. Cornwall makes replacement inserts so we are going to replace the other  9 before we head out again. And we have to get this electrical stuff resolved.

All in all, RVing is always an "adventure" lol!

Ain't RVing an adventure!   Actually, it was the Ford V-8s and V-10s that were made from 1999 to about 2004 that had the spark plug issues (I used to have one). Apparently, there weren't enough threads in the heads for the plugs to hold onto. Few people reported any problems until the plugs were changed. Then, if the new plugs weren't torqued properly, they could work loose and blow out of the head. I seem to remember that aluminum inserts were Ford's recommended fix if the warranty had expired.

Good luck with the electrical issue and let us know how it goes.

Kev