My 2003 Itasca has electrical problems the house batteries dont charge, the 12v lights in the coach do not work unless on shore power or generator

make sure disconnect is on and make sure no fuses blown

Your question and facts are a bit terse. Usually when shore power is present you can leave both house and chassis batteries connected so they are charged/maintained by your charger/converter. Using a multimeter, test all parts of the 12v circuits to be sure the converter/charger is outputting at least 13v to house and chassis batteries.

you need to use a multimeter and check solenoids. does it have power when motor or generator is running?

There is a relay that operates when you hook up to shore power that switches from battery power to converter power. It also charges the batteries. If you do not have battery power then suspect a faulty relay. It is located inside the power converter.

Contact your local retailer/service center directly or online here

connect your disconnect

If the unit has a transfer switch that switched between generator and shore power you need to look at that since nothing is working with the unit plugged into shore power. There may also bee a few battery disconnect switches close to the batteries. In that system there should also be a few inline circuit breakers. If they have tripped they will need to be reset. To determine if they have tripped you will need to look at the circuit breaker and see if there is a small black lever hanging down. If there is, slide it back up and it will lock back into place and should restore power. Without actually seeing the coach and the power configuration it is difficult to determine exactly the problem. Hope this helps.

You are probably hearing the cooling fan cycling. The fan is controlled by the temperature which is controlled by the amp draw which produces heat. If you are using your refrigerator, water heater, AC and lights then you are drawing a heavy load on the converter. I know that the water heater, AC and refrigerator may use 100 electricity but they also require 12v power to run the circuit boards.

You might unhook the battery and with the camper plugged in to shore power the 12v lights should work. If not check the breaker that goes to the inverter. If that is not tripped then check the power output at the converter. I would expect the inverter is shot. I replaced the one on my Jaco two years ago with (Progressive Dynamics 60 Amp Power Converter with Charge Wizard and the remote pendant)

You will not have electricity while on battery power. Two different systems. Electric is 110VAC and battery is 12VDC. If on battery power the lights will work, the furnace will work (LP gas and 12v blower motor), the refrigerator will work (LP gas and 12v power for circuit boards) and the water heater will work (LP gas and 12v power for circuit board). The only way to have electricity while on battery is to install an inverter but you will need extra batterys and still will not have enough power to run the AC for any extended length of time.