Furnace Control Board Has No Power

I can run the fan on continuously but when i put the heat to on on the t stat the 5 amp fuse on the control board lh33wp003a in the furnace blows.

Furnace control board has no power.

What would cause electric furnace circuit board to fail. 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. Measure from r to w. Either way check to make sure you have the proper input voltage to the board.

If your electric furnace is blowing a fuse repeatedly when turning on your first step should be to call in an experienced hvac repair professional. First make sure you have power to the board. If you have 24 volts and no light on board. Heat mode goes strait to trouble code bad ground open ignition circuit also no power from board to induction motor.

Fan only operation is running. Check for 24 volts to board from transformer. Just went thru the flow charts from rheem on that furnace. You should see 24vac.

You have bad board replace it. You should see 24vac. With the stat in off mode. If so it will need to be replaced.

In some cases this will be line voltage and in other cases the board will get its power from the control transformer. 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. 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. Power up transformer cool mode works blower stays on after temp is reached.

Measure from r to c at the control board. The electric furnace transformer may be failing causing the system to short. Next you want to check the output and this is a little more involved than the previous step. A model number of the furnace would be helpful too.

Don t forget when the blower door is open. The sequence is like this.