I have a GMP Series Gas Furnace heating and central AC unit. I noticed a few months back the blower comes on randomly even if the thermostat is off. I removed the thermostat thinking it was defective. The thermostat wiring block was not touched. The blower still comes on. It seems like the unit is getting a signal to turn on but only the blower turns on. This happens in both the heat and AC mode. I think it may be the control board. Any ideas?

Tom

Possibly the fan relay that's on the control board switch is bad.

XenoSapien