Nest pro keeps turning ac on and off

[EE2]

Does anybody know why my nest keeps turning on and off my a/c ?

[itemdefect]

I have the same issue. I received a Nest Learning through the LADWP rebate program and the thermostat randomly turns on and off the A/C when the Thermostat, Google Home App, and Nest App say the thermostat is set to OFF mode. Only way to actually turn off the A/C is to unplug the Thermostat from the base. When I reconnect my old manual thermostat it works fine, turning on only when it should be on. Only thing I can think might be causing an issue is that my HVAC has two zones with two thermostats on a single unit but I only have Nest installed on one and the other is still has an old, manual thermostat. Any advice/help will be greatly appreaciated

Attached are photos of the old wiring and the new. The black wire is actually the white wire with some heat shrink over it.

New Wiring and A/C goes off when thermostat is set to OFF modeOld Wiring and Working

[Ryan_G]

Hey folks,

Thanks for reaching out here in the Google Nest Community.

With your description of the issue, it is possible that your Nest Thermostat is not getting enough power from the HVAC unit. We could resolve this problem by connecting a C (common) wire to your Nest Thermostat. 

We could check if there's a unused wire from the HVAC system that we could use as a C wire.

Best,

Ryan

[itemdefect]

Hi everyone,

So fortunately, I had a Blue and Brown wire in the wall unused on the old thermostat since it was battery powered, and the Blue-C wiring to the HVAC was already set. After connecting the Blue wire to the C terminal on the Nest base my Nest no longer turns on and off the HVAC randomly, even when it is set to OFF. So it fixed this issue.

Only issue now is when I set to COOL, I hear the HVAC turn on but kind of in a half power state. Usually I hear this sound initially before what seems like the main fan kicks in.

[Ryan_G]

Hi itemdefect,

Thanks for reaching out here in the Google Nest Community.

It's good to hear that connecting a C wire resolved the issue of activating the HVAC randomly. For the cooling issue, we could check the wire from the Y terminal and make sure that it is properly connected.

Also, could you share a photo of your current wiring configurations?

Regards,

Ryan

[Ryan_G]

Hey folks,

I just wanted to follow up and see if you're still in need of help. Please let us know as we would be happy to answer any questions you may have. 

Best regards,
Ryan
 

[itemdefect]

Hi Ryan,

Thanks for following up.

My nest is now fully functional. When I reconnected the old thermostat and noticed the HVAC still didn’t work, I knew  something is now wrong with the HVAC. I found out that an important wire in the HVAC got loose when I took off the panel to check for the C-wire connection. Once I reconnected the wire my Nest activates the HVAC properly.

[Ryan_G]

Hey itemdefect,

Thanks for the reply.

It's great to hear that everything works fine now. We'll keep this thread open for the next couple of days and let us know how it goes.

Regards,

Ryan

[EdwardT]

Hi itemdefect,

I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any trouble from here, as I would be happy to take a closer look and assist you further.

Thanks,

Edward

[EdwardT]

Hi itemdefect,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,

Edward