Second stage cooling not activating

[LewisWilliams]

Installed a brand new 3rd Gen learning thermostat. All tests run fine except second stage cooling. My AC just groans and stalls and never gets going. 

Have a two stage AC and gas furnace, about 20 yr old Bryant models. Re: wiring I have originally Rh with jumper to Rc, G, W, Y, and Y2 (blue wire). I plugged the wires into the same corresponding terminals for the thermostat: Rh, G, W1, Y1, Y2 (again, blue).

First had to figure out that my first 3rd Gen thermostat had a bad battery. So I'm on my second Nest in three weeks. At least this battery is fine. 

[LewisWilliams]

Sorry not sure how to post photos. Here are links to the before and after.

https://www.flickr.com/photos/41605477@N04/53849350033/in/dateposted-public/ 

https://www.flickr.com/photos/41605477@N04/53849529190/in/dateposted-public/ 

[LewisWilliams]

Here's the power info:

• Battery, 3.674 V
• Voc, 36.90 V
• Vin, 29.88 V
• Iin, 20 mA (i)

[LewisWilliams]

Hi anyone have suggestions?

[AxelD · Accepted solution]

Hi LewisWilliams,

Thanks for posting in the community! Sorry to hear that the second stage cooling isn't kicking on in your Nest Thermostat. No worries, help is here! Here you have some recommendations that might help to fix this:

1. Install a C-WIRE or a Nest Power Connector: est thermostats typically need a C-wire for continuous power. Without it, the thermostat might not have enough power to function properly, including utilizing the second stage. 
2. Go to Settings > Equipment > Wiring > Set Y2-WIRE as second stage cooling.
3. Contact a Local HVAC technician or Nest Pro to check the wiring on your system.

Let me know how it goes.

Regards,

Axel. 

[LewisWilliams]

Thanks for the info! I am first having an HVAC repair person take a look at the system. Will report what I discover.