Installed Nest Thermostat. app says wires not detected. Not cooling. Compressor not starting

[nmcnetto]

I started replacing a Trane XL824 thermostat with the Nest Thermostat.

I connected all the wires as required, but when I ran the app it said it could not detected the G and the W1 wires

I checked the wires and they are good, and the tabs remained down.

The app allowed me to continue the setup and everything. However, only the ventilation is working. The compressor is not starting, so it is not cooling my home.

HVAC was working before.

Help!

Thanks

[aperezdeleon]

Hi there nmcnetto,

Thanks for reaching out to our community.

Thermostat installations can get complicated sometimes because you need to consider several factors. However, let's see what's going on.

Do you have a picture of the wiring for your previous and current thermostat? It would also be great if you could let me know what type of system your thermostat is controlling.

If your Nest thermostat has removable batteries on the back, I would suggest trying to set the thermostat again. However, if it gives you the undetected wires message, remove the batteries, do so for about 5 minutes.

Even though you've already checked the wires, it wouldn't hurt to turn off the power and make sure they are clean and free of corrosion.

Let me know how it goes.

Regards, 
Angel.