Rudd Furnace under-achiever 90 no lights nothing power going to unit and 3 amp fuse check out OK! I had the board, and blower replaced today ran for about two hours and now nothing again!Same problem! Help.

Send direct power to the blower by bypassing relay . See if motor runs

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Hello my name is Heath it will be my pleasure to assist you. First thing to do is go to the furnace take off the lower blower door and locate the circuit board turn the power off to the furnace. In the circuit board there should ba a small car like fuse usually 3 or 5 amps check the fuse it is probably blown replace the fuse with the same amperage fuse and then turn the power back on on the furnace and check the operation of the furnace.

Hello my name is Heath it will be my pleasure to assist you. First thing to do is go to the furnace take off the lower blower door and locate the circuit board turn the power off to the furnace. In the circuit board there should ba a small car like fuse usually 3 or 5 amps check the fuse it is probably blown replace the fuse with the same amperage fuse and then turn the power back on on the furnace and check the operation of the furnace.

Hello my name is Heath it will be my pleasure to assist you. First thing to do is go to the furnace take off the lower blower door and locate the circuit board turn the power off to the furnace. In the circuit board there should ba a small car like fuse usually 3 or 5 amps check the fuse it is probably blown replace the fuse with the same amperage fuse and then turn the power back on on the furnace and check the operation of the furnace.

Hello my name is Heath it will be my pleasure to assist you. First thing to do is go to the furnace take off the lower blower door and locate the circuit board turn the power off to the furnace. In the circuit board there should ba a small car like fuse usually 3 or 5 amps check the fuse it is probably blown replace the fuse with the same amperage fuse and then turn the power back on on the furnace and check the operation of the furnace.

See if you can locate the control board. There should be an automotive push in fuse on it. It should be a small amp fuse around 3-5 amps. Check it and change if needed. You should be able to see if it is blown or not just by looking if you don't have access to a multi-meter.
The control board is usually located in the blower compartment. Thank you.

Some circuit boards have a built in transformer and others have the transformer that sits right beside the board depending on the age of the furnace. First, look for a small 3 or 5 amp fuse on the circuit board. Check it, and if its good, and you have a small ohm/volt meter. Check your transformer. You can either ohm it out or just check for voltage. You have a "high" voltage side and a "low voltage" side of the transformer. The "high" voltage side will go to the power (120 volt) that comes into the furnace. This would probably be the side that would burn out during an elec. storm. To ohm the transformer: (This will be your best way to check)

1) shut off power to the furnace
2) pull the two wires loose that go to the "high voltage side"
3) put the leads from your ohm meter to each wire that goes to the transformer, and you should get some kind of reading. If not the "high voltage" side of the transformer is burnt out

You can follow those three steps to the "low voltage side as well, just remember where you take any wires off.

Be sure you have the power turned OFF. Good luck, hope this helps you.

When you set the the switch to ON, I'm assuming that is the fan control? You should leave that on AUTO. The furnace will turn the fan on when the heat exchanger reaches a preset temperature. Which will prevent COLD air from coming out of your vents.

First find the electronic control board. Is the diagnostic light on and flashing a code? If not look for the automotive type fuse on the board. It is a 3 amp. Is it blown? Next look for a screw in fuse in the ssu switch on the side of the furnace. Is it blown? If all the fuses are good is the door switch behind the front cover working? Is the door properely installed? If all these items are working, you should have power to the furnace. If these items are ok, check for 24volts at the transformer. Check the terminals not black and white. If you have voltage there, remove the red and white thermostat wires on the control board. Next take jump wire and jump the red and white terminals. This rules out the stat and stat wiring. Your furnace should start. Check the status light for any further problems and crossreference the flashing light code to fix.

the fuse that your refering to is on the control board indie of the furnace. shjould be a 3 amp. good luck.