Furnace Control Board 3a Fuse Blowing

Assuming this is a fuse on the low voltage side coming off the 24 volt transformer it s possible the contactor in your condensing unit has shorted out causing it to blow the fuse.

Furnace control board 3a fuse blowing.

When a thermostat wire touches the metal frame of the furnace it can deliver more voltage than the wires are designed to handle. Go to outdoor unit. This will blow the fuse on the control board causing the draft inducer to not start which then stops the rest of the furnace functions from working properly. The most probable of these are 1.

I know there is a short somewhere and i ve read on multiple posts to remove the wires from the 24 volt terminal block w r g c y and start putting them back one by one until the fuse blows again and then you ll find your problem. 1 disconnect all thermostat and outdoor unit control wires from the terminals on indoor unit control board turn thermostat to call cool and see if fuse blows if it blows the control board in unit is shorted and will need to be replaced if not move to step 2. 2 reconnect all wires previously disconnect at control board.