topic Re: Nest Thermostat A/C kicks on then immediately turns off in Nest Thermostats

Nest Thermostat A/C kicks on then immediately turns off

Nico757 — Fri, 02 May 2025 01:21:17 GMT

Hello all!

I recently switched to the Nest thermostat in February and have been having great success managing my power/gas bill as a result.

The season is heating up so I have attempted to switch on the A/C but every time I try to switch to A/C the unit cuts on for a second then immediately powers off. On my thermostat it immediately displays a message "Wifi disconnected" and starts a timer to retry starting the AC. It continues to fail.

I have pictures of the previous model and wiring and I appreciate any help to avoid having to call expensive service! Thanks to the community!

Re: Nest Thermostat A/C kicks on then immediately turns off

Patrick_Caezza — Fri, 02 May 2025 03:21:52 GMT

@Nico757

Can you post the pictures of the original thermostat's wiring and one of the Nest base plate wiring?

If the camera icon isn't showing, you can use an image hosting site like Imgur's upload page and then copy/paste the link it provides.

Re: Nest Thermostat A/C kicks on then immediately turns off

Nico757 — Fri, 02 May 2025 03:56:15 GMT

Hello Patrick! Here is the original thermostat wiringOriginal Thermostat Wiring

Re: Nest Thermostat A/C kicks on then immediately turns off

Nico757 — Fri, 02 May 2025 03:57:16 GMT

And here is the Nest wiring

Re: Nest Thermostat A/C kicks on then immediately turns off

Patrick_Caezza — Sat, 03 May 2025 01:32:25 GMT

@Nico757

Interesting way they wired it originally.

Can you look in the furnace and post a picture of how the Thermostat terminal block on the control board is wired?

Re: Nest Thermostat A/C kicks on then immediately turns off

Nico757 — Mon, 05 May 2025 19:00:12 GMT

Hello @Patrick_Caezza I have more pictures if needed! Here is what I have so far please let me know if this is what you are looking for!

Outdoor wiring #1

Outdoor wiring 2

Outdoor wiring #3

Re: Nest Thermostat A/C kicks on then immediately turns off

Nico757 — Thu, 08 May 2025 00:10:51 GMT

Hey @Patrick_Caezza let me know if my photos helped you please!

Re: Nest Thermostat A/C kicks on then immediately turns off

Patrick_Caezza — Thu, 08 May 2025 04:35:55 GMT

@Nico757

I need to see what the brown thermostat cable is connected to in the furnace. I don't need to see the outdoor units' wiring. The furnace can be located in a small closet, in the garage, or in the attic space, to name a few locations.