Furnace Control Board Has No Power

The ac power is disconnected.

Furnace control board has no power.

First make sure you have power to the board. Either way check to make sure you have the proper input voltage to the board. You have bad board replace it. Furnace control board fuse keeps blowing 1 answers hi i have a carrier furnace 48gs 036090311tp with a honeywell t8401c thermostat.

A model number of the furnace would be helpful too. If so it will need to be replaced. Just went thru the flow charts from rheem on that furnace. The electric furnace transformer may be failing causing the system to short.

It is possible that the problem could stem from your electrical system rather than the furnace itself but your hvac system is the best place to start. Fan only operation is running. Next you want to check the output and this is a little more involved than the previous step. What would cause electric furnace circuit board to fail.

Heat mode goes strait to trouble code bad ground open ignition circuit also no power from board to induction motor. You should see 24vac. Power up transformer cool mode works blower stays on after temp is reached. With the stat in off mode.

The sequence is like this. If your building s electrical system supports 120 volts your furnace needs a transformer to convert to the correct voltage to run the controls ignition and timers. Changed control board in gas furnace new board has no power to transformer blower motor lead on cool terminal hot all the time all the safety switches ohm out. In some cases this will be line voltage and in other cases the board will get its power from the control transformer.

Measure from r to c at the control board. You should see 24vac. Make sure the 110v power switch at the air handler furnace has not been turned off then see if the fuse on the board at the air handler is not blown automotive type then there is a safety switch. Don t forget when the blower door is open.

Measure from r to w. Check for 24 volts to board from transformer.