Nest Gen 2 to Gen 4 - heating when on cool

[Mozzie2025]

Just replaced Nest Gen 2 with Gen 4 (have heat pump). Copied wiring setup used in Gen 2, but it's heating when on cooling. How do we fix this?

Y1, G, OB, RC, Y2 Aux, C

[Mozzie2025]

Resolved: Found suggestion to go to Settings - Equipment - Heat Pump and switch from O to B (or vice versa) via the Home app. That seems to be working.

[jenniffert]

Hi Mozzie2025,

Thank you for posting in the community! I’m glad to hear you solved the issue with your Nest Learning Thermostat (4th gen). Adjusting the O/B wire setting is a key step for many heat pump systems, as it determines how the reversing valve functions. I appreciate the update and your sharing this valuable information with the community.

If you need more assistance in the future, feel free to post again.

Best regards,

Jenniffer