Generac 4800 starts only on shore line

[nicklogan]

I recently bought my first RV, a 96 Europa and have been going through it to fix various issues. The PO told me the generator didn't work and I thought he was right as I got no response from the dashboard start switch with the key on or engine running. However, I was surprised that it did start and provide power when the dash switch is used if I'm plugged in to AC power. Once it's started it will continue to run with the AC power unplugged. All the fuses look ok. Can anyone suggest what to check?

(First post!)

[OldToolmaker]

Check the state of charge of your house batteries. Heck, figure out which battery set is used to start your generator. Happy hunting.

[twinboat]

You may find that the battery that starts the generator is dead but the charger running off AC shore cord gives enough power to start it.

[nothermark]

What he said. House generators typically start off the house battery bank. That bank usually is connected through a storage relay. Many systems automatically close that relay when plugged into shore power so the converter can charge the batteries. I would start by looking at why the genset does not have starting power. It could be as simple as that relay is not activated by the storage (salesman) switch or it could be a real mess.

My first check would be if the lights work when not plugged in as they are usually controlled by the storage switch position. If the lights are on and the generator will not turn over I would be looking for power that was not there on battery but there on shore power as I worked my way through the starter power chain. If the lights are on but trying to start the generator causes them to fade out I would be looking at the house batteries including poor connections.