I have an Intertherm model MGHA-056AAFC-05 propane furnace with pilot light in a park model trailer.Its 12 years old and used sparingly.Almost since day one it will intermittantly fire up with a blow torch sound and when the blower motor cuts in... the flame will go out and it will shut down.
I can overcome this problem by catching it when I hear the blow torch sound and by turning the thermostat back,cutting off the gas valve... then keep resetting it until I no longer hear the blow torch sound and I have a clean burn... then all is fine and it will go through its full function.
Some times the blowtorch sound won't appear for a minute or 2 after the gas valve has opened,but most times its immediate... Is this a sticky valve?Or possibly a venting/draft problem.

Many different things can cause this problem. A bad propane gas regulator comes to mind first. It could be the maintank or the house regulator or the one in the gas valve on the unit. Since this is propane I suggest you have a professional On Site service call to find the exact problem. Your propane dealer would be your first best choice since it could be there regulator causing the problem.

Propane is a very unforgiving gas that can and will go BOOM at the slightest provacation so I suggest you have it checked out before further usage.