Noise when A/C is shutoff at Thermostat - http://www.hvacmechanic.com/ Forums

Original message

texas76

65.248.47.143

"Noise when A/C is shutoff at Thermostat" , posted Wed 16 Jul 11:40

My oustide Trane unit makes a screeching noise when I turn it off at the thermostat (even if the unit is not running). Any ideas on what this might be? It seems to be cooling okay (not super cold, but as cool as I remember alway being) and it does not make the screeching noise when the outside unit shuts off on its own.

Replies:

Houston204

98.196.66.53

"Re(1):Noise when A/C is shutoff at Thermostat" , posted Wed 16 Jul 19:07

Heatpump reversing valve releasing, causing suction and discharge pressure to equalize.

It should sound kinda like bus brakes.

"Tip of the Day" Remember to remove power first.

texas76

65.248.47.143

"Re(2):Noise when A/C is shutoff at Thermostat" , posted Thu 17 Jul 09:02

Thanks so much for the reply. Is this something that will eventually give out and need to be replaced? Is it related to the compressor or something else?

Houston204

98.196.66.53

"Re(3):Noise when A/C is shutoff at Thermostat" , posted Thu 17 Jul 21:08

While I cannot hear your unit to verify that it sounds no worse than most... Heatpumps make this noise when they are turned off. They are not normally turned off at the stat, so not many people are bothered by this. It is not necessarily a sign of an upcoming failure.

If it sounds worse than you feel it should, a service call might be worth it, for peace of mind.

I believe the Honeywell RTH7400 will maintain the reversing valve in the last required position when you turn it off.

"Tip of the Day" Remember to remove power first.

texas76

65.248.47.143

"Re(4):Noise when A/C is shutoff at Thermostat" , posted Fri 18 Jul 09:20

Thanks again for the reply. I think I'll just quit turning off at the thermostat (which I used to do all the time) and let it ride for now.

Best

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