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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 14784
Experience:  15yrs in the HVAC industry with certificates and degrees.
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I have a TRANE XE 78. Here is what I have replaced thus far

Customer Question

I have a TRANE XE 78. Here is what I have replaced thus far -
1. Board 50A50-405 with 50A55-486
2. Capacitor for blower
3. Transformer C340041P01 (was buzzing)
- Blower runs in high speed in "ON" position from thermostat indefinitely.
- Blower runs in "auto" position in call for heat mode. Board flashes rapidly. Furnace fire and runs perfectly.
- Blower runs for 20 seconds in "auto" position in A/C mode. Blower winds down. stops and then starts back in low speed. Copper on unit frosts up.
- Blower runs in "ON" position indefinitely until A/C mode turned on. Runs for 20 seconds, winds down, stops and starts back at low speed.
– After turning unit of at Thermostat and turning fan back to "ON" only, it will only run slow speed. If left off for 5 minutes, then turn fan to "ON" position it will run high indefinitely.
We have the same thermostat upstairs and down. I have switched. It is not that. I have checked and rechecked the thermostat to furnace wiring and all checks out.
Is it the fan motor? Nothing else left. Thanks in advance. Tim
Submitted: 11 months ago.
Category: HVAC
Customer: replied 11 months ago.
A/C portion of unit was replaced 3 years ago, inside and out. Could low freon cause this symptom? I know that the copper frosting up is typically a sign of low refrigerant. Is it a safety so the unit doesn't freeze up and destroy parts?
Expert:  HVAC Guru replied 11 months ago.

Hello, one minute while I get some information together.

Expert:  HVAC Guru replied 11 months ago.

Hello and thanks for using this service! If you are a JA Member I would like to personally thank you and welcome you back! I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly, I do not know your skill level so please try and let me know if I am going beyond your knowledge or comfort zone thanks! I strive for a 5 star rating from everyone especially our JA members.

Answer:

Tim this is a bad ECM blower, replace the fan on the unit and it will work fine again.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

Customer: replied 11 months ago.
Since it runs in the "ON" position in no mode , but not in the A/C mode means the two speed blower motor in shot in the high speed range?
Customer: replied 11 months ago.
It was the only thing left to change. Thanks
Expert:  HVAC Guru replied 11 months ago.

Yes

Customer: replied 11 months ago.
Greatly appreciated.
Expert:  HVAC Guru replied 11 months ago.

No problem

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am paid anything through the site and that will also get you a DIRECT LINK emailed to you to get back to me!.....tips are greatly appreciated so thank you very much for using this service. If you have any other questions just post back to me here anytime!

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