I have a fairly old gas A/C central air unit which was working fine until last night. When the A/C unit was switched on (I live in Southern Cal.) I noticed a burning smell (electrical) which I tracked down to the unit in our basement. I immediately switched the system OFF at the control panel but there was obvious arcing still taking place around the circuit board wiring so I immediately removed the power at the circuit breaker... which stopped the arcing/burning. I also switched off the gas input for safety reasons.
My question: would it be worthwhile replacing the circuit board and surrounding wiring or will I have to replace the entire unit. There have been no other issues with the system, either cooling or heating up until now but I obviously don't know what caused the problem in the first place! What are the costs likely to be for either course?
Gus

