Taking over an existing nest thermostat

[OnlyShawn]

Hey y’all. I just purchased a home that has two central air units. I know both of them work well, because they were runnning when we saw the home when it was for sale and it was FREEZING.

when I purchased the home and set up my WiFi to connect to the thermostats I reset them both (to remove previous owner accounts) and set them up as new by telling them that the wires that were connected (the nest wire tag colors) were the wires from the existing thermostat. 

but it doesn’t seem like they’re running correctly. I definitely am not getting heat from the lower unit (and I tried the toggle O/B wire in settings), and it also doesn’t seem like I’m getting cool air. 

so how do I find what wires exist in the system to set up nest without knowing how the original thermostat was wired?

[Markjosephp]

Hello OnlyShawn,

Congrats on your new home! It's great that you're proactively setting up your Nest Thermostats for optimal comfort. Troubleshooting HVAC systems can be a bit tricky, but let's try to figure this out together.

Firstly, for the lower unit not providing heat, double-check the wiring to ensure everything is properly connected. Make sure the wires correspond accurately with the Nest Thermostat. If there's any doubt, you might want to refer to the system's manual or consult with a professional HVAC technician. For the cool air issue, there are a few things to consider. Check if the air filters are clean, as dirty filters can impede airflow. Additionally, verify that the settings on your Nest Thermostat are configured correctly for cooling mode.

Since you mentioned trying to toggle the O/B wire in settings, that's a good step. Ensure it's set appropriately for your system (O for most systems, B for some heat pump systems). If the problem persists, it might be worth it if you could perform a factory data reset and reconfigure it back to the app.

Let us know how it goes.

Best,
Mark

[OnlyShawn]

Turned out it was a bad capacitor on the outdoor condenser, so it wouldn’t turn on. 

Completely unrelated to wiring. I’d pulled the panel cover off to look and make sure the wiring from the control board was ask accounted for

[Markjosephp]

Hi OnlyShawn,

I'm glad you were able to identify the issue with the outdoor condenser! It's interesting how troubleshooting sometimes leads us in unexpected directions. I appreciate you checking the wiring from the control board too, even if it turned out to be a capacitor problem. It's all part of the diagnostic process. If you have any more details or questions, feel free to share.

Thanks,
Mark