Thermostat won’t stay on Cool mode.

[Mrmcfish]

I had an 10 year old nest learning thermostat. It suddenly wouldn’t stay in cool mode or cool/heat mode. I was trying to cool the house and it kept automatically changing to heat mode and shutting off the AC. I thought the thermostat went bad so I replaced it with a 3rd gen learning thermostat. It seemed to work for a week but now it won’t stay on cool or cool/heat mode again. It stays in cool or cool/heat for up to 5 mins then automatically switches to heat. The house temp was 74. I was trying to get it down to 72. It kept turning to heat. I’ve turned off auto schedule. I’ve turned off eco. Need help.

[CoolingWizard]

Check your setting for ECO and Safety Temperatures.

Ken, The AC Cooling Wizard

[Jhonleanmel]

Hi folks,

Chiming in to see if you still need assistance with this. Let us know if you have additional questions ― we'd love to help.

Best,
Mel

[Markjosephp]

Hello Mrmcfish,

Checking back in — how's it going? Still need our help? Let us know so we can assist you right away.

Best regards,

Mark

[Markjosephp]

Hello Mrmcfish,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any additional questions or concerns before I lock this thread in 24 hours.

Thanks,

Mark