Trying to start generator trips shore power breaker

[Sunovabeach]

I have a 5500 Onan Marquis Gold Generator. I went to auto start it and after a few clicks, shore power breaker tripped. Checked batteries and unfortunately fluid was low. Could batteries cause shore breaker to trip or is it a Microprocessor card issue. - Help please.

[okcnewbie]

I believe you're supposed to start up the genset without AC loads. If you haven't tried it that way I would. That would isolate the input (12VDC) from the output (120 VAC).

There's a chance you could start the RV and try to start up the genset while the rv is running.

As far as the shore power tripping;

The batteries would only tie to the shore power through the converter. It seems unlikely to me that the batteries could cause the shore breaker to trip. I suppose if you're already close to the current limit and the battery voltage dropped and the converter went to max charge you could pop the breaker.....maybe!

[luvlabs]

Please tell us the make, model and year of your coach.

Do you not have a transfer switch? It's purpose is to isolate the incoming A/C shore power from the generator. You are supposed to start the generator without A/C loads to protect the transfer switch from premature failure as most transfer switches are set to default to generator power.

Other than to supply power to start the generator, they should be out of the loop until the generator is running.

[Sunovabeach]

2011 Itasca Sunova 33C.

[Sunovabeach]

The autostart indicator flashed a microprocessor failure. I believe it has a auto transfer switch, however not at my seasonal site right now to check. Reset 50 amp breaker to shore power, and all works. haven't tried to start it once I topped off the deep cycle batteries.

[FreedomDream]

With the shore power back on, the batteries should recharge.

The description of the problem sounds like it could be an automatic transfer switch issue. Automatic transfer switches are suppose to default to the generator so that even with being plugged in to shore power, the generator should start and after it is running at full speed, the ATS will put the coach on generator power.

Whenever starting any generator, be sure any significant loads are turned off. Only turn on air conditioners or microwave, toaster or space heaters after the generator is running at full speed.

[TQ60]

Shore power and generator should never interact so stop what you are doing and make some checks.

If you had a dead battery and charger was pulling high current combined with other loads like ac then maybe but as others stated maybe transfer switch issue.

So follow these suggestions but be very careful and maybe have a helper there just in case.

Suspect something wrong with transfer switch and to be really safe have helper be inside operating genny and you measure on outside and do NOT touch the mh just in case you get hot skin as it could kill you.


Turn off everything and remove shore cord from outlet and place it on a table or box so not resting on ground.

Get a voltmeter.

Have helper start genny and without touching the plug measure voltage across EVERY COMBINATION of pins looking for any voltage.

You should see nothing as the transfer switch should isolate this.

If you do then look at transfer switch.