Originally Posted by NorthernHeat
I would hope your furnace had a 5 year part warranty. It is very rare that a PC board would fail in only 4 years, but voltage spikes and lightning hits can ruin one in no time. I'd call the company who installed it, you should only have to pay the diagnostic fee, and labor, maybe $125.00. I hope the person who came out doesn't do HVAC for a profession, this doesn't sound like a hard problem to diagnose. Also, it is very unlikely from you symptoms that this problems has anything to do with the outside unit.