Trane XB80, no blower motor on command

chvbob

Here goes. Went to use furnace this year, the unit would not work. Done some checking, and found out that it was kicking out on high limit. Discovered the circulation motor was not coming on, so the unit overheats, and kicks out on limit.Tried to run the fan manually, and got no response. Pulled fan unit out, and found a bad capacitor. Replaced, and cleaned fan, and reinstalled. The fan still did not come on, but i could run it direct. Checked all wiring to make sure there was not something i hooked up wrong. I found a troubleshooting sheet, and ran through the step by step checkout. It ended with it saying the control board was bad. The board was just replaced last year, but i replaced it anyway. No luck, same thing. Checked pressure switch, high limit switch, flame sensor, and multiple wires for continuity. The unit will start with the inducer motor, then ignite, and then kick out on high limit. The fan is able to be controlled with the t stat on both the heat, and cool side. Unit will function ok if i leave the fan running constantly with a different power source. And there you have it. That is where i am at. I can keep operating the fan till i get it fixed, but i doubt that it is a good idea.

beenthere

Check if heat terminal on board has 120 volts when it should.

chvbob

Checked all that. 120 volt side, and 24 volt side have their respective voltage. Board just doesn't supply voltage when called for after the allotted time is up for the turn on. I do hear a relay click at the time that the fan should come on.

beenthere

Thats what I meant for you tom check, if the heat terminal has 120 volts, if not, its usually a board problem. if it does, its a motor or other wiring problem.

chvbob

I understand what you were saying, sorry if there was a misunderstanding. Would be a little wierd to have aboard that is one year old, and a new board, to have the same problem though. Possible i suppose, but my son has not had a return problem with this board.