Got home from the Brewer game this afternoon and noticed the house was warm(78). Outside was 91. I checked the T-stat and it was set correct. Noticed the air vents weren't blowing anything. Went outside and the condensor and fan was running fine. Then I went downstairs to the furnace unit to see what I could find out. Seems like power is going into the transformer but not coming out to fan motor. Didn't check with volt meter, just a electricity present pen? Don't know the correct name for that gadjet but I like it.
The blower motor and capacitor were replaced this past winter by me(the previous one was 6+yrs old). In June I had a service call because A/C condenser was not kicking in and blower was running constant. Turned out there was a blown 30amp fuse outside and inside the technician wrapped on the transformer with a screwdriver because it wasn't clicking in and out like it should be. After he did that he said it was working correctly. I wouldn't have believed it had I not been watching him. He said this is what caused the blower to run constantly. He said this might need replacing or it could go for awhile. I told him to leave it be. While he was outside he also spotted a worn contactor and asked me if I wanted it replaced and I said sure. I'm thinking it's that transformer that needs replacing. Looks like it one seperate piece on top of the electrical box on inside of unit frame(right side). Any Help is appreciated, Thank you. The unit is a Magic Chef(1988).

Phelixu

labman

Do you have the blower relay and transformer mixed up? Transformers may hum a little, but never click. If the outside compressor is running, the transformer is fine. However, the relay could have been stuck closed and opened in response to the screwdriver. It could be not working at all now. Check to see you have AC to the relay plus 24 volts to the relay coil, the pair of smaller wires, maybe red and blue to it. If so, and don't have AC to the blower, the relay is bad.

justdoit2

I am experiencig similar issue with Bryant furnace. tested Motor & Capacitor. Both look good. Trying creating a shot situation - using R & G. Still din't kick off the blower motor.

Seems relay is bad. What is the best way to fix the relay? replace whole PCB?

Any help is greatly appreciated.

Thx.

acetc

The board would need to be replaced if the fan relay is bad.

justdoit2

thanks. that was the reason. I ended up replacing the whole control unit.. cost came out 240 bucks.