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Machinc
Machinc, General Contractor
Category: Home Improvement
Satisfied Customers: 817
Experience:  Has written home improvement articles since 2008. Earned South Carolina Residential Builders License in 1991.
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I've got a Trane XE80 (TUD120C954J0) and the blower fan

Customer Question

I've got a Trane XE80 (TUD120C954J0) and the blower fan doesn't activate manually or in heat mode. I replaced the blower motor and capacitor but that didn't clear the problem.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yes, thermostat settings are correct, and filters are new.
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: No Oh I did measure the voltage off the transformer, it's 28V but rated at 24V
Submitted: 23 days ago.
Category: Home Improvement
Customer: replied 23 days ago.
Also, turned on the fan at the thermostat and could hear a relay click from the control board accompanied by a loud buzzing (louder buzzing, there's always a buzz when the unit has power), but then couldn't measure any voltage between the motor neutral (E11 CIR-N) and any of the 4 motor hots (E17 COOL-H, E16 HEAT-H, E28 PARK, E27 PARK)
Expert:  Machinc replied 23 days ago.
The buzz you hear is the transformer . It will often be audible when the unit is idle.
Expert:  Machinc replied 23 days ago.
The parts you replaced control the operation of the motor but so does the relay.
Expert:  Machinc replied 23 days ago.
The relay can operate ( the clicking sound) but still not send power to the fan.
Expert:  Machinc replied 23 days ago.
The relay "contacts" can be bad or dirty. They also can be worn down where they don't make good contact.
Expert:  Machinc replied 23 days ago.
Replacing the relay will likely solve your problem.
Expert:  Machinc replied 23 days ago.
The relay should remain operated the entire time the fan is supposed to be running.
Expert:  Machinc replied 23 days ago.
You can locate the relay by its "clicking" when it operates or tries to operate.
Expert:  Machinc replied 23 days ago.
The relay has constant voltage on one side and when it operates properly it should have the same voltage on both sides.
Note : this is the high voltage contacts.
Expert:  Machinc replied 23 days ago.
Do not confuse with the low voltage contacts (24/28!volts) it only is present when the relay is "called" to operate.
Expert:  Machinc replied 23 days ago.
It also should remain constant when the fan is supposed to be running.
Expert:  Machinc replied 23 days ago.
The fact that you are hearing the relay click is a good indicator the low voltage part of the circuit is working properly.
Customer: replied 23 days ago.
Upon removing the board the back of it was charred and one of the relay contacts had burned a 1/4" hole in the back of the board and destroyed the solder terminal. Ended up replacing the whole board because of it, but the relay was definitely the problem. Thanks!
Expert:  Machinc replied 23 days ago.
Glad you found it .
Best to you , good repair job.

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