Newly installed Nest does not have Cool Mode

[christine2]

We just installed a new Nest  and there is no cool mode (just heat). The wires we have are Rc, C, and W1. Here is what the wiring looks like:

This is what our old Ecobee wiring looked like:

Any idea what could be wrong? We've tried re-inserting the wires, performing a factory reset, turned AC power off/on, etc. Thank you!

[Daveed]

I was running into the same issue, the PEK cable from the second photo it's unique to ecobee. If you look at this diagram from the ecobee website, you'll see that the PEK connects to the Y in the furnace:

I did the following:

- Turn off the power for the thermostat
- Plug the PEK cable into the Y slot
- Do a factory reset to the Nest thermostat
- Run the install process again, this time checking the Rc, C, W1 and Y1 boxes in the app
- Turn the power back on

That got me control of both heat and AC from the app.

[Patrick_Caezza]

You have to remove the PEK device that is installed by the air handler/furnace as it is not compatible with the Nest. 

You are probably going to need to replace it with the Google Nest Power Connector which does the same thing, but for the Nest

[MelbaDT]

Hey folks, 

Thanks for your responses, Daveed and Patrick_Caezza. 

christine2, I'm jumping in to check if everything is good here. Let us know if you have more questions. 

Best, 

Melba

[MelbaDT]

Hey christine2, 

Checking back in ― how's your thermostat now?

Best, 

Melba

[christine2]

Hi, yes, Daveed's answer solved my issue. Thanks to all who helped!

[MelbaDT]

Hi christine2, 

Awesome — glad to hear that. I'll go ahead then and lock this thread then after 24 hrs. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community.

Cheers, 

Melba