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2 Nest Learning thermostats stopped Stage 1 cooling

Docnejeres
Community Member

‎08-07-2024 08:36 AM

I have 2 Nest Learning thermostats, one installed 2 years ago no problems; the second installed 3 months ago also no problems. Both stopped Stage 1 cooling 1 week ago. Both cool fine on stage 2, but very inadequate for the summer heat and house size. Checked all wiring ok, even tried unplugging the Y2 to force Y1 and complete reset of both systems, disabled home/away, Eco, learning features. Re-installed. Both systems use C wire, no G wire.

Complex set up. I have 2 large Mastercool Evaporative 2 stage cooling systems on separate circuits that I have installed PCB control units. First system has single dedicated transformer. Second system has dual transformers, one for AC, one for the furnace.

Very strange that they both stopped Y1 function at same time, separate installs, separate circuits; almost like a software issue (Did check for updates, all UTD), Any Help is appreciated!

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jenniffert
Community Specialist
Community Specialist

‎08-10-2024 11:03 AM

Hi Docnejeres,

 

Thanks for posting in the community! I'm sorry to hear that your AC isn't working as expected with stage 1 cooling. I'd be happy to help.

 

To better assist you, please share a picture of your wiring installation and provide the following information:

 

  • What type of HVAC system do you have (conventional or heat pump system)?
  • When did the cooling last work on stage 1?
  • Have you received any error messages?
  • Did you verify if the fan and heating still work as expected?
  • When was the last maintenance and cleaning service?
  • Is this the first time you're using cooling this year? If so, did heating work without issues during the winter?

In the meantime, check the air filter. The HVAC system needs good airflow to work properly. A clogged air filter can restrict airflow over the cooling coils, which can cause them to freeze and shut down the system.

 

Also, ensure the wires are fully inserted into the terminal and the connector buttons are securely pushed down. This guarantees proper wire connections. For reference, you can check out this article: Troubleshoot strange heating or cooling behavior. Important: Before touching any wires, turn off the power to your HVAC system at the breaker box. Then, please go to Settings > Technical Info > Power on your Nest Learning thermostat and provide me with the VOC, VIN, and IIN values.

 

Please keep me posted.

 

Best regards,

Jenniffer

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