Don't know your model, but on the left hand side on the top is usually a small electronic module, have a look in there for signs of burning, I think most 12v htrs will only come on when the engine is running, the pipe at the rear top should get hot if either heater is working. Also you ought to hear the gas igniter sparking in time with the flashing and when a good flame is established the thermocouple should leave the gas on after removing pressure from the push button
Norman
January 2009
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