Cannot find cooling mode on nest

[viveksharma1204]

Hello,

I installed my new nest replacing the old Honeywell thermostat and when I go to mode it only shows heat and off. How do I add cooling to the modes?

Thanks for your help.

[jb76 · Accepted solution]

Hi - you can display both Heat and Cold (assuming you have AC) by going into the Nest app. - open the Thermostat device (tap) and at the bottom of the screen there should be a 'Mode' - make sure to select 'Heat * Cool' and then you will be able to see both modes on the app. and on the Nest thermostat. If you don't see 'Heat * Cool' as an option to select you will need to go through the thermostat Equipment setting and select to test Heat, Fan, Cool to verify connectivity to your 'Cool' AC/compressor. For a typical furnace/AC, the following wiring should be connected:
W - Heat/Furnace control
R - Power to/furnace control
Y - Cool - control to AC/compressor
G - Fan control (unconditioned air to turn on)
C - Optional but good to have to keep the Nest charged (needs to be above 3.85 V to be controlled and send signal to your furnace/AC). This voltage can be checked in the Technical Info  of the Nest (under 'gear' icon of the Nest app.).
J

[viveksharma1204]

My Google nest thermostat is not showing on Google nest app but instead on Google Home. In the mode, it is only showing heat and off options.

Also, for the wiring, I have Green, Black, White and Red but no yellow.

[jb76]

Hi - You may need to confirm this on the furnace controller board but the black wire may be connected to the Y port of the furnace to control the AC/compressor. Make sure to turn off power to the furnace/AC/thermostat (usually its own breaker) and then try connecting the Black wire to the 'Y' connector of the Nest baseplate. Restore power and reconnect the Nest thermostat controller (attach to baseplate) and it should detect the Cool/black wire connection. You can also go into the settings option in the Nest thermostat menu (choosing the gear icon) and then go to Equipment-->Test and go through testing Heat, Fan, and Cool. Note any issues doing these tests and reply with the error code (s) and the connection display of the wiring found by Nest when you went in to test Heat, Cool, Fan.

[viveksharma1204]

Hello, thanks a lot for your advice and I did that and connected my black wire with Y slot and it is showing the option of cooling mode.

thanks a lot.

quick question, since there is no C wire connected now and my thermostat has batteries in it, hope that won’t affect anything?

[jb76]

Without a C wire…it will run for now getting its power to charge the Nest battery every time you run the furnace/AC. Over time though the Nest battery will degrade to the point it won’t keep enough charge to control heat/cool and connect to wifi. There are a couple of options to address this though:

1. Purchase/install a Nest Power Connector kit:

https://store.google.com/us/product/nest_power_connector?hl=en-US

2. Run a new 5 wire 18 gauge thermostat wire from the Nest to your furnace control board (may not be easy to do depending on access to furnace, location of existing wire, walls etc). There are mixed reviews installing/using the NPC in terms of providing enough power to the Nest  to keep it above 3.85 V (min. power level for full functionality). Personally, I was able to replace the thermostat wire bundle and get full 24V power over the C wire to my 8 year old Nest (3rd gen Learning Thermostat).

You can check the charge level of the Nest in the app (Settings —> Technical Info) or under Settings - >Power on the Nest thermostat itself.

Good luck!

J

[zoeuvre]

Hi folks,

@viveksharma1204, I want to check if you managed to see the response above. Also, the Nest Thermostat, which operates on batteries, can function properly without a C wire connected, as it provides a constant source of power. However, advanced features like power-hungry settings and continuous Wi-Fi connectivity may have limited functionality or drain the battery more quickly without a C wire. Additionally, low battery levels can impact the thermostat's overall performance and functionality. 

Please let us know if you still have questions or concerns, as we'll be willing to assist you more. 

Thanks for your help, @jb76. 

Best,

Zoe