1988 Coachmen Leprechaun 12v Electrical Problems

First thing to check is usually the ground. Quick and dirty, try a jumper cable , bat negative to a good ground point see how it does then. Since you seem to be having whole system problem with voltage, corrosion on the ground strap would be the first suspect.

Consider cleaning the battery grounds as well as the generator ground - make sure the battery is fully charged - and if you start the engine before trying to start the generator it should put both the engine and house batteries on-line to assist in starting the generator. That should rule out whether you have battery issue.

Thanks, I'll try those suggestions as soon as I can

With basically no load, you should see very nearly the same voltage at the generator as at the battery. A bad ground connection would be a very good place to start. Bad connections in general at and around the battery would be next in line.

Note that the generator starter is, in general, the most demanding instantaneous load you'll place on the house battery unless you have a fairly large inverter. Mine takes around 90-100A when cranking. It doesn't take too much of a poor connection to have a significant voltage drop at those currents.

It's going to be either the ground wire at battery or where it hooks to the frame. Or the hot wire connection at battery or generator.

Dusty

I just discovered that the house battery disconnect latching solenoid on our rig was not working because of dead house battery. I started the truck engine and the engine's alternator raised the voltage in the house battery so that when I pressed the house battery disconnect switch there was a loud snap. I shut the engine off and then there was 13.2 volts at the battery terminals, indicating that the converter charger was working properly on 110vac shore power. A fully charged house battery should read over 13 volts, 12.5 volts may be too low to start the generator, voltage drops under load of generator starter trying to start the generator. If you start the engine, the voltage in the house battery should rise to around 14 volts and the RV generator may start. If you use the starter switch on the RV generator itself, it may start more readily than pressing the generator switch on your inside control/monitoring panel. Using the "emergency start" switch on your dash board connects house and starting batteries in parallel, which may start your generator, also may start the truck engine when the starting battery is low/discharged. Check electrolyte levels in house battery(s) and starting battery, add distilled water as needed to cover the plates with a rubber bulb filler. Clean corrosion from battery connections, make sure to connect all wires with ring terminals to the same battery terminals. When plugged into shore power, with converter charger working properly, and house battery disconnect switch in the on position, you should read over 13 volts at the house battery. With truck engine running you should read over 14 volts. Voltages are dependent on condition of the house battery and good clean/tight connections at battery terminals and good ground cable to frame connection.