HELP: A/C stops cooling after a period; Resets works then it stops again.

[NestHeadache]

I installed Nest 2 years ago, and since then, this issue has been puzzling me...

Initially, when it ran on cooling mode, it worked fine, but after 2-3 weeks, the outdoor A/C compressor would stop running. Thus, it was still blowing strong but not cooling the house. I reset the circuit breaker to switch off the blower (including wires connecting to Nest), waited for a few minutes, and then powered it back on, and the A/C would be cooling again. Heating mode has been working okay with Nest.

In 2021, I requested an HVAC service specialist via Nest to diagnose the issue. He inspected my A/C unit carefully but didn't find anything wrong and only recommended "trying to turn the presence sensor off," which I did.

Recently, this issue is happening almost every day. I noticed the A/C compressor mostly stops running during midnight. It's super annoying when it's still blowing air all the time but not cooling the house when I am still in bed.

I hired an A/C professional yesterday who again inspected the A/C units carefully but didn't find anything. The refrigerant, motor fan, filter, etc., everything is working okay.

I am using an Amana A/C. The error code I got is L2: HPCO lockout (3 Trips) when it stopped running.

I have attached photos. Please let me know if you have had the same experience and how I can fix this.

Nest

The outdoor A/C unit

[Jfguajardo]

I have the same issue. Had my AC inspected by 2 different companies and found no issues but seems the Nest cools intermittently. 

[Markjosephp]

Hello folks,

Thanks for reaching out to the Google Nest Community Forum. I'd love to know more about this.

Power-related issues, the system may need professional maintenance, and there may be an issue with the changeover valve are some of the possible causes for your HVAC system to deactivate unexpectedly. To isolate:

• When was the last maintenance check for your HVAC system?
• Have there been any recent changes or upgrades to your HVAC system?
• Does the issue happen with heating only, cooling only, or both?
• Are there any error messages? If so, what are they exactly?
• Gather the power readings in the Power Info section of your actual thermostat's Equipment settings.

Keep me posted.

Regards,
Mark

[Jfguajardo]

Hi Mark. Service was done July 28th. The technician didn’t find any issues. Just cleaned the unit on the roof. He said he thought the nest might be the issue. I’ve only experienced this with cooling as in Texas right now we’re in the 100s daily so no need for heating. No error messages. I started a chat with nest support and they determined my nest was defective. If I swapped the wires and turned on the heat it would begin cooling. I bought an installed a new nest and will keep this post updated if I have any issues. 

[Markjosephp]

Hey Jfguajardo,

I appreciate you reaching out to our support team and for still keeping up with the Nest Thermostat. In the meantime, you can still use your thermostat to control your Cooling unit while waiting for the new one to arrive. So please don't hesitate to give us a shout if you need more help. 

Thanks,
Mark

[Jfguajardo]

I replaced the unit with a brand new one as the Google tech-support said my old one was defective and the new one has the same issue. It will cool for a little while and then intermittently stop cooling but if I reverse the wires of cold and heat, it starts working again.  I think I’m done with nest. Wanna just returned this new one and get something else.

[NestHeadache]

Hi Mark,

Here is more info FYI: 

• When was the last maintenance check for your HVAC system?  - In July 2023
• Have there been any recent changes or upgrades to your HVAC system? - No
• Does the issue happen with heating only, cooling only, or both? - Only with cooling
• Are there any error messages? If so, what are they exactly? - No error displayed on Nest. Ran the code on the A/C unit when it stopped running before resetting, it's L2 as "HPCO (High Pressure Cutoff)". 
• Gather the power readings in the Power Info section of your actual thermostat's Equipment settings. - See attached below. 
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