Generator shuts off if a 12v source is not present.

[Belleauwoodsman]

Hello everyone, new to this stuff but not new to camping. I have a 2000 newmar mountain aire 37.5ft with onan marquis 5500. I'm horrible with electrical but my generator will start and run if it's either plugged into shore power or the chassis engine is running. But I think I have it narrowed down to a box in the hood compartment with genny running and engine running i press the use switch and can start genny at itself or the remote start at the dashboard. So if i shut the chassis motor off within 30sec i hear a clicking in the hood area and generator will shut off. If plugged into shore power genny starts and runs when unplugged genny dies. I have a few other issues but can start a new thread for it. Any help or guidance is greatly appreciated because this is sounding expensive.

[MrWizard]

Dies when shore power is unplugged
Converter is working on shore power
Why is converter not working from generator power
When it should be ?

Check and reset the generator circuit breakers

If you start generator when the drive engine is running
And shore cord is unplugged, do you have 120v power to your outlets ?

Replace house batteries, they are dead, they should have supplied 12v control and fuel pump power for the generator
Generator is hard wired to batteries,
It does not go thru battery control center or disconnect storage switches,

[wa8yxm]

The generator uses 12 volt for control and to run the electrical fuel pump.

IF there is no 12 V No joy

The house battery on most RV's provides the 12 volt till the auto transfer swich kicks in and then the converter provides it

ON SOME Rv's the chassis battery provides the 12 V

and on a very few it has it's own battery

IF the converter is Non op. or if the batteries are not connected. You may see what you see.

on the rare occasion or was it 2, that I killed both house and chassis batteries on this rig I "jump started" the Genny.

Keep jump battery hooked up till ATS does it's thing and converter comes on line. (Took me a couple tries to figure that out)

I carry isolated batteries for this (Jump pack 2 of 'em on in house one in car).

[Lwiddis]

“but my generator will start and run if it's either plugged into shore power or the engine is running.” I’ve never run my generator when plugged in or driving.

[enblethen]

Could be as easy as tripped 12 volt DC circuit breaker or blown fuse

[jdc1]

Your house batteries are toasted. Or the wiring to said batteries is bad.

[enblethen]

Dead house battery or battery disconnect is tuned off. Power is coming to genset through the charge relay.

[K_Charles]

It sounds like the battery is no good but you say "with genny running and engine running i press the use switch and can start genny " I don't think the generator will start if it is running so please reword that give more info.