topic Re: AC shuts off when it shouldn't and then turns right back on in Nest Thermostats

AC shuts off when it shouldn't and then turns right back on

horseshoehorn — Wed, 08 Jun 2022 03:37:21 GMT

Nest Gen 3 was installed 3 months ago and everything worked fine until recently. Now, maybe once a day, the entire AC unit will turn off when it shouldn't and then turns right back on 5 seconds later. The thermostat says "Cooling" and the fan is running but the outside unit doesn't turn on because of 5 minute time delay module. This causes the thermostat to get stuck thinking it's cooling when it's not and never shuts off and never cools.

Wiring is yellow wire to Y1, green wire to G, white wire to W1, red wire to Rh (4 wires, no C wire).

Re: AC shuts off when it shouldn't and then turns right back on

Patrick_Caezza — Sat, 11 Jun 2022 06:13:05 GMT

Move the wire in the Rh terminal to the Rc terminal.

There is a very good chance you will need to install the C wire. Check and see if there is a spare wire at the thermostat, if not then you can use the Nest Power Connector to make a C wire.

Do you still have a picture of the original thermostat's wiring?

Re: AC shuts off when it shouldn't and then turns right back on

MelbaDT — Thu, 16 Jun 2022 01:44:17 GMT

Hey folks,

Thanks for responding, Patrick_Caezza.

horseshoehorn, I'm jumping in to check if everything is good here. Have you tried Patrick's suggestion above? If yes but to no avail, kindly provide the photo of the wiring requested so we could keep the ball rolling.

Best,

Melba

Re: AC shuts off when it shouldn't and then turns right back on

horseshoehorn — Thu, 16 Jun 2022 15:35:37 GMT

This is how it was wired.

Re: AC shuts off when it shouldn't and then turns right back on

horseshoehorn — Thu, 16 Jun 2022 15:42:41 GMT

This is how it is now wired per Patrick's suggestion.

Re: AC shuts off when it shouldn't and then turns right back on

horseshoehorn — Thu, 16 Jun 2022 15:44:52 GMT

Because the problem is very intermittent, I am still evaluating if this solution works.

Re: AC shuts off when it shouldn't and then turns right back on

MelbaDT — Fri, 17 Jun 2022 03:40:26 GMT

Hey there,

Got it — thanks for getting back to us. Let's keep this thread open for a few more days so we could observe it further.

Keep us posted.

Best,

Melba

Re: AC shuts off when it shouldn't and then turns right back on

horseshoehorn — Sun, 19 Jun 2022 14:22:13 GMT

I am still having the issue, but it is slightly different. Now the fan will turn off and right back on (very intermittently), but the outside unit will continue to cool. I assume it never shuts off because otherwise the delay module would activate.

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Fri, 15 Jul 2022 05:25:17 GMT

I am having a similar issue in that the compressor will shut off for a few seconds and then turn back on. Looking at the history of runtime, this error occurs most often when there is a programmed, lower temperature change. The thermostat does not begin the time delay in order to protect the compressor. I am using the c wire.

Re: AC shuts off when it shouldn't and then turns right back on

usalbeash — Thu, 04 Aug 2022 03:04:15 GMT

Hi I’ve had my nest for 2.5 years working fine. Now it’s doing the same thing mentioned in this discussion, except! My fan on my furnace is the only thing shutting off. the outside unit is still running. Then the fan will come back on and the thermostat says 25 mins to cool. No I do not have a C wired on my thermostat. Nor have I for the past 2.5 years. My battery is 3.858 ,VOL37.32,Vin 34.90, lin 40ma. This has just started this summer. It will even do this if I put the fan in Manual for 2 hours. It will still shut it off and turn it back on. Wiring is Y1-blue, G-green, W1-white, Rh-red.

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Thu, 04 Aug 2022 02:56:34 GMT

The software was last updated on May 4th. This can't be a coincidence. Mine is showing Version 6.2-27. Regarding a solution, I ordered a new thermostat from a competitor of Nest.

Re: AC shuts off when it shouldn't and then turns right back on

usalbeash — Thu, 04 Aug 2022 03:06:15 GMT

I’m thinking of doing the same thing , I agree with you.

Re: AC shuts off when it shouldn't and then turns right back on

usalbeash — Thu, 04 Aug 2022 03:13:43 GMT

You are onto something! I do know mine does this if I drop my thermostat by 2 degrees. It did it tonight and I hadn’t touched it. I bet it got behind by 2 degrees though? I’ll monitor that

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Thu, 04 Aug 2022 03:21:41 GMT

https://www.googlenestcommunity.com/t5/Nest-Thermostats/Nest-Gen-3-turns-off-and-back-on-within-a-few-seconds/m-p/208259/emcs_t/S2h8ZW1haWx8dG9waWNfc3Vic2NyaXB0aW9ufEw2NFhSUDAzRkw5VkJKfDIwODI1OXxTVUJTQ1JJUFRJT05TfGhL#M41764

Re: AC shuts off when it shouldn't and then turns right back on

usalbeash — Tue, 09 Aug 2022 10:34:10 GMT

I ran a C wire to the furnace and it fixed the issue. My battery 3.943, Voc 33.92, vin 36.67, Lin 200ma(c) hope the info helps

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Tue, 09 Aug 2022 12:29:06 GMT

I connected the C wire a few weeks ago and it has not resolved all of the issues. At 3:00 in the morning, the schedule drops in temperature. The system will shut down at this time and turn back on.

Re: AC shuts off when it shouldn't and then turns right back on

Ryan_G — Thu, 11 Aug 2022 11:04:25 GMT

Hey Engineer,

Thanks for the reply.

Were you able to restart or reset your Nest Thermostat after you've connected the C wire?

Regards,

Ryan

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Thu, 11 Aug 2022 22:37:21 GMT

Hi Ryan,

I rebooted the thermostat after I added the C wire. I did not reset it to factory settings.

Re: AC shuts off when it shouldn't and then turns right back on

Ryan_G — Tue, 16 Aug 2022 10:50:27 GMT

Hi Engineer,

Thanks for the reply and for doing the suggested steps.

I'd like to know how it's going after the reboot. If you're still getting the same result, we recommend doing a complete data reset on your Nest Thermostat.

Let us know how it goes by replying to this thread.

Regards,

Ryan

Re: AC shuts off when it shouldn't and then turns right back on

Engineer — Wed, 17 Aug 2022 21:44:56 GMT

Hi Ryan,

I did the reboot before I posted anything. All of the issues have been since I rebooted the system. Consequently, I just reformatted the system, per your suggestion. I will let the system learn before I manually make any adjustments. I'll follow up in a few weeks.