the heater was working only when it wanted to. suspected that there was a short in wiring Last week the heater came on and would not shut off even when the car was turned off. A local repair shop said that there is a battery under hood and it pulled it to shut heater off and that a new module would be need for $420 - this is a 1991 - don't know if he is scamming me or not. How can I find out if this true and how do I find out where this battery is - so I can replace it and pull it if this problem happens again. It only affects the heater. I am 73 years old and feel they were conning me. Charged me $40 just to pull plug which took less than five minutes.