HVAC Questions? Ask an HVAC Expert for Answers ASAP
Not sure why you have 2 transformers unless you have a humidifier or U.V tied into the system using the other transformer, but these transformers are fed 120v from the board high voltage terminals and then in turn the 24v from the transformer goes back to the board to power all of the 24v circiuts. If you have 120v going to the transformer but no 24v coming out of the transformer then it is bad. If you have 24v coming out of the transformer but no 24v on any of the functions coming out of the board using 24v like the thermostat (should have 24v between R and C at all times) then the board is bad or the 3 or 5 amp fuse on the control board is blown.
I think you're correct the one transformer powers the humidifier valve/control.
I'll verify that.
What can keep the fan from running when I use the "run" over-ride on the thermostat?
No power to the motor because of a bad control board, bad transformer, or the 3 or 5 amp fuse on the board is blown
You said that you can manually jump 120v to the motor and it runs so we know that it simply is not getting the call to run from the board
Fuse is good. Transformer is good so based on your input it must be the board...right?
One final test will tell us
and that is?
take a jumper wire and connect the G terminal on the control board to the R terminal on the control board and then press the door saftey switch in
If the motor doesn't come on bad board. If the motor does come on bad thermostat (or thermostat wire)
OK, I'll try that and let you know in a few minutes....It's hot in the attic so I'll try to be quick.
Looks like bad board....no joy on the motor running jumpering G to R.
yeah if you hot wire and the motor runs with direct power then there is no problem with the motor or the capacitor. Jumping G and R bypasses the thermostat so if there is 24v at the R and C terminal and the motor doesn't run then it is the board.
OK, thanks. Any recommendations on where to get a good price on board relatively quickly?
If you buy it online your going to have to wait for shipping. Best bet is to call a Tech most of the good ones carry a universal board for these 50A55 boards.
OK, thank you...have a great (remainder of) day!
that is the board that shows up as the replacement for the 288