As the heading says I bought a used Goodman GMP 100-4 and the red light on the board blinks 4 times. As soon as power is turned on tho the Furnace I hear a click and a few seconds later the blower motor and inducer run even with the thermostat disconnected. I have checked the inductor switch and have continuity, and also tried jumping it. I checked the nipple on the inductor and it is clear, the hose is not kinked. The vacuum pot does open and close when vacuum is applied. the fuse on the board is good. I did not see a reset button any where. Also there is a multi connection plug laying in the bottom of the Furnace and I have no idea what it is for. See photo I just happen to think I have not checked the igniter. It will do the same with the thermostat connect or out of circuit. Am I missing something, is the board the problem. applied.
The plug in bottom of the furnace had come unplugged from the board. Plugging it back in solved the problem.
That plugs into the board shown. Have you checked the heat exchanger in that thing? They had issues from the factory. Odds are you bought a paperweight with that furnace.