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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Trane air handler unit, installed in 2003, model

Customer Question

I have a Trane air handler unit, installed in 2003, model TWE042C140C0 which is having start-up issues. When it kicks on I hear the unit try several times before it stays on and runs. I can hear the blower start to run then it kicks out and restarts then repeats this cycle normally four to five times before it stays on. A local service tech said either the control board or thermostat (no - I was not impressed with that "insight") was causing the rapid cycling. I can't find the control board part number to replace it (service tech quoted $825) - have almost no documentation on the unit and haven't found any online.
Does this sound like a board issue (can see slight discoloration on the board and it is original) and if so, can you help me find the replacement part number?
Thanks ---- Bob F, Downingtown, PA
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, so far it sounds like the compressor contactor is 13 years old and has burnt contacts. ($70 item) or needs a hard start kit installed or both, ($100 item), however I am not clear yet on *what is taking 4 or 5 attempts to start... the compressor, or the fan motor.

If its the fan motor with the problem, it could have worn out bearings by now, or a weak run capacitor.

We can go from there.

Customer: replied 1 year ago.
The indoor air handler blower fan is what I hear starting and stopping - the outdoor unit seems to start up okay and run without issues. He did check the blower unit capacitor and it passed, although he didn't give me the actual numbers. It seems like the blower tries to start then clicks off and immediately tries to start again - cycles 4-5 times then decides to stay on. Either an intermittent signal from the thermostat (3 years old) or the control board developing some type of failure causing it not to stay on?While it is 13 years old it is lightly used since we almost never use the air conditioning in the summer - largely a heat only winter time use October - March.
Expert:  Phil replied 1 year ago.


You will need a clamp around type amp meter to diagnose this effectively,

$25 at harbor Freight, $50 at a big box electrical dept. Check the amp draw on each wire separately going to the motor as it is attempting to start... and the run capacitor. That will isolate the problem either to the relay on the printed circuit board or the motor itself.

We can go from there.