W have a suburban camper heater. Sometimes it will ignite and work but sometimes it won't. We have had a repairman out here many times that seem to fix it and then it does it again... HELP:(

That is a 12 volt system. They have spark ignition, blower delay, and other parts to make them approved for use in a camping trailer. This board usually does not cover this type of furnace but I can give you a pointer or two.

When you pull one out for service (yes in order to do it correctly you have to pull the entire furnace out of the coach or trailer).
Next pull the burner and clean all the rust and dust out of the combustion chamber and while you have the gas train out clean the orifice on the main burner and the pilot.
Next you need to fire the unit up on a work bench. A 12 volt battery and a garden gas grill tank with adapter is all you need for this operation. When you put the 12 volts to the unit it will start and if not you start checking for failed or intermittent components.

Most of the time I find that little ants have made a home in the pilot or main orifice and that is easy to clean up. If that is not the case the you have to start checking the air flow switch, circuit board,combustion motor or any other parts for failure.

They are very easy to work on but you have to know what you are doing.

I think you need to find a different repair person that actually knows how to clean these out and repair them.

Good luck.

PS do not forget to jump the thermostat wires for the test phase and you might need a new little gasket for the gas train attaching flange.