topic Re: Replaced Honeywell with Nest 4 - Heat Pump system - Now will not come on in Nest Thermostats

Replaced Honeywell with Nest 4 - Heat Pump system - Now will not come on

jwinters99 — Thu, 12 Mar 2026 22:01:51 GMT

Replaced Honeywell with Nest 4 - Heat Pump system - Now will not come on. I checked the 5 amp fuse in the system and its still good. I can turn the fan on using the app. The compressor never kicks on and nothing else does either. Please help. Ive added pics of old and new. I have since taking this pic removed the black wire from the * terminal. I did go in the attic and check the existing wiring. the black and white are tied together. Im lost.New - current black wire removed from *Original HoneywellAttic connectionsAttic connectionsAttic connections

Re: Replaced Honeywell with Nest 4 - Heat Pump system - Now will not come on

jwinters99 — Fri, 13 Mar 2026 00:06:43 GMT

Slight update. Since removing the black wire I now get a click at the condenser outside for both a heat cycle and a cool cycle but it never does anything beyond that. Just a click/clunk and that’s it.

**Revised** Inside unit appears to come on, i can hear it kick on and i can hear/feel the air coming from the vents. It appears that only the outside unit is the only thing not working. Still just the clink/clunk.

Re: Replaced Honeywell with Nest 4 - Heat Pump system - Now will not come on

StephanieQ — Mon, 16 Mar 2026 22:02:25 GMT

Hi @jwinters99,

Thank you for posting in the community! I understand that your Heat Pump system hasn't turned on since you replaced your Honeywell thermostat with the Nest Learning Thermostat (4th Gen). I appreciate the troubleshooting steps you’ve already taken and for providing those pictures. It’s helpful to know the fan works through the app and that disconnecting the black wire allows you to hear the condenser and feel air through the vents. I know this setup process can be frustrating, but I’m happy to provide some information to help you move forward.

Based on the pictures and information provided regarding the system type and setup, I suggest contacting a technician to check your system and the wire connections on the control board. You can use the link below to find a Nest Pro in your area who is trained to ensure the proper installation and functioning of your system: Get professional help setting up your Nest products.

Hope this information helps!

Best regards,

Stephanie