I have a Payne 376C downflow model furnace. I live in So California so my furnace operates only five months a year. Two years ago when I turned on the unit in October the heating component worked fine but the blower would not come on. The repairman I called in told me the blower was kaput and I needed a new furnace. After he left I bypassed the circuit board and found that the blower worked just fine. I pulled the circuit board and saw a dark solder spot, resoldered and reinstalled and the unit worked just fine all winter. Last year same thing: no blower, pulled circuit board, resoldered, good all winter. Today I turned on the furnace and guess what? Same thing. Assuming I find the solder bad again, what could be causing such? Why good on the last cold spring day and bad by the next fall?

Should I just buy a new circuit board? ($200 - $300)

MANY thanks.