Nest Errored Out, then blasted heat while errored out...

[N3stN00b]

Hey all,

Not too long ago I had an issue with the nest thermostat blowing heat on cool, and after paying for an hvac technician to come out... it was concluded that the base on the nest had gone bad and needed to be replaced.

Thankfully Google was good about this and got me the replacement bases. However 2 months later... I've been noticing the thermostat randomly erroring out saying that wires were not detected when nothing has changed. I verified that nothing was triggering the overflow causing such errors and all was fine.

Restarting the thermostat / removing and attaching the thermostat to the base eventually fixed this issue.

Fast forward to today, I woke up and the house is a blistering 89 degrees (mind you it was only on COOL mode the whole time). I take a look at the thermostat and it had the E75 error: no heating or cooling. connect W1 or Y1 wire.

What doesn't make sense to me is while this was errored out, the thermostat was set to full blast the heat. Why would you not cut the power to the O/B wires when the thermostat errors out?

I'm at a loss as to what to do, I want to replace the thermostat but I dont want to deal with these issues especially having a run-away HVAC system if I'm not at home to stop it. Is anyone else experiencing these issues?

[jenniffert]

Hi @N3stN00b,

Thanks for posting here in the community! I understand how inconvenient it is when your Nest thermostat is providing an inaccurate temperature. I'd be happy to help!

I also appreciate all the information provided. To better assist you, I'd like to ask the following:

• What is the model of your Nest thermostat?
• Would you be able to share a photo of the wiring installation?
• What's the make and model of your HVAC equipment?
• Are all the wires securely plugged into the terminals, with no loose or exposed wires?

Please keep me posted.

Best regards,

Jenniffer

[N3stN00b]

Hi jennifert,

Thanks for chiming in.
- It is a gen 3 nest thermostat
- Wiring is fine, has been untouched and functioning for a while

- Hvac unit is a lennox heat pump (dont remember model off the top of my head)
- All wiring is fine, I even unplugged and replugged just to be safe.

Im fairly certain its the nest unit or base (unlikely since it was just warrantied).
As of now I have removed all Nest products from my home since I cannot trust these units to not kick on the heat and boil everything inside.

[jenniffert]

Hi @N3stN00b,

Thanks for following up! I apologize for the delay and appreciate all the information you provided. Let's try to fix this!

Error code E75 means the thermostat isn't detecting the W1 and Y1 wires. In this case, I'd suggest the following steps:

• If both W1 and Y1 are connected, clean them with a paper towel (dust can affect detection). Important: Turn off the HVAC system at the breaker box before checking the wires.
• Ensure the little buttons next to the terminals are fully pushed down.

For more information on Nest thermostat error codes, you can refer to this article: Troubleshoot Nest thermostat help codes.

I also suggest trying to change the O/B wire settings for your heat pump's orientations. For instructions, refer to this article: Troubleshoot heat pump issues. In addition, if you can share the model of your HVAC system and what wires you have connected to the base, it would be very helpful to determine compatibility with the Nest thermostat.

Let me know how it goes.

Best regards,

Jenniffer

[N3stN00b]

Hi jenniffert,

I really appreciate your assistance, however I have tried literally everything. I have since removed the nests and replaced it with the original thermostats, everything functions as intended.

It is likely the nest base failed on me again, or the thermostat itself is bad.
If anyone needs a discounted nest thermostat feel free to check your local fb marketplace, I will be giving them away as they are unreliable and a waste of money / time.

[jenniffert]

Hi @N3stN00b,

Thanks for the information. I'm sorry to hear that the steps didn't resolve the inconvenience with the Nest thermostat.

I appreciate all your efforts. I'd like to take a deeper look into this for you. Please fill out this form with all the needed information, and then let me know once you're done.

Please keep me posted.

Best regards,

Jenniffer

[jenniffert]

Hi again, @N3stN00b,

We haven't seen your submission form come through yet. Were you able to access it okay?

Let us know if you're running into any trouble or still need our help!

Best regards,

Jenniffer