First the unit has gone haywire running fulblast at high heat.I think the unit broke as I was replacing a standard convenience outlet with a GFRC outlet. I did not turn off the circuit breaker thinking it was a simple task. I did not know that the furnace was connected to the same circuit and as soon as I connected the last wire to the GFRC, I heard a loud noise from the furnace as if the motor was made to start rapidly. Then the heater went on fullblast on high heat. I was not able to turn it off through the thermostat so I just pulled the plug off from the receptacle. I plugged it in several times but the unit went on at high speed and high heat. I finally turned off the gas and unplugged it for two weeks. I plugged the furnace back on, turned the gas on and lit the pilot light but the furnace won’t even start even though the desired temp was set at max. The fan motor is fine when manually tested.

Could it be that the transformer or the gas valve is broken?

I need help. Any tip is appreciated. Thank you.