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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 atrane XV90 that screaches when the furnace comes on,

Customer Question

I have atrane XV90 that screaches when the furnace comes on, especially on chilly evenings. Trane service technicians have check or replaced all motors but have not found a solution. What are possible causes?
Submitted: 1 year ago.
Category: HVAC
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now. Please give me time to respond as typing, researching and adding links takes me time to do so please be patient and often I will ask you questions to narrow down the issue to get is diagnosed correctly.

How loud and how long does the screeching last?

Customer: replied 1 year ago.
Can be heard throughout a 2 story house easily, for15 to 20 seconds.
Expert:  HVAC Guru replied 1 year ago.

If you remove the panel on the furnace and run it does it make the same noise?

Customer: replied 1 year ago.
It happens more frequently now that it gets chilly at night, stating more frequently after sundown. For example, when the outside temperature drops, a screaching noise comes from the furnace at varying intervals, after the blower motor has started. Last night the furnace made the screaching noise at least 26 times between midnite and 7 am. We could not sleep. During the daytime today it has not occurred much.
Expert:  HVAC Guru replied 1 year ago.

Can you remove the panel on the furnace to see if that continues to make noise?

Customer: replied 1 year ago.
NO furnace blower motor, at least, stops when the bottom panel is removed.
Expert:  HVAC Guru replied 1 year ago.

Yes can you just tape the panel switch down and run it like that to see if that stops screeching?

Customer: replied 1 year ago.
Do you mean the levers that are used to open the panel door?
If not, I don't know where the panel switch is. As soon as I remove the outside panel door, the furnace blower turns off.
Expert:  HVAC Guru replied 1 year ago.

Yes there is a switch that the panel engages when put back in place. That switch should be right up in the corner on the frame edge you should be able to see it.

Customer: replied 1 year ago.
We have to wait for the screaching to try to turn of the switch. If the screeching stops then what will that tell us? One problem that we have is that the screech lasts for such a short time that by the time we get down the stairs to the furnace the screeching usually has stopped. Sometimes we can sit by the furnace for a long while and nothing happens especially during the daytime.
or Are you asking if the screeching stop stops when the panel is not on the furnace?.
Expert:  HVAC Guru replied 1 year ago.

This may be a whistling noise from the suction through the ductwork at start up, it will not do that if you have the panel off and if it does not then there is a suction issue through the return vents.