[mholl]

i have a goodman gmp 100 and the main blower comes on at will with the thermostat off . it may cycle on for awhile one day and then not again for a couple more days or it might cycle on and off all night.the only way to stop it is to kill the power. could this be a bad board ?

 

[NickTech]

sure, a bad board may present these symptoms. there are other culprits that may be responsible for the problem. there may be bad wiring from the t stat to the fan relay control in the furnace causing this to happen. the hi limit my be tripping off due to hi temp in the furnace, as well as the hi limit going bad, which will trigger the blower motor to come on.

 

[mholl]

where is the hi limit located?

 

[NickTech]

Behind The Gas Valve, Mounted On The Rear Wall Of The Furnace. It Is A Black Square With 2 Terminals Coming Off It. There Is A Thermistor Limit Mounted To The End Of An 8 Inch Extention.