E77 Error y1 not detected

[Rimfeld33]

We are just turning on a/c for the season and have an error E77. We don’t use the system winter.  So we have used the system wired to y2 and not y1 with a heat pump. Did something change? 

[AxelD]

Hi Rimfeld33,

Thanks for posting and sorry to hear about this situation with the cooling on your Nest Thermostat. No worries, help's here! Let's try changing the O/B wire settings. It's possible they're currently set for heat instead of cool. Here are the steps:

• Nest Thermostat 

1. Open the Home app Google Home app
2. Tap your thermostat.
3. At the top right, tap Settings .
4. Select Thermostat.
5. Scroll until you find Heat pump. It should show which wire configuration is currently selected.
   If the O option is highlighted, select B.
   If the B option is highlighted, select O.
6. To make sure the issue is resolved, test your heating and cooling again.

• Nest Learning Thermostat and Thermostat E

1. On your thermostat, go to the Settings Nest settings icon.
2. Select Equipment.
3. Select Continue and then Continue.
4. Select Heat Pump.
5. The Nest Thermostat defaults to an O setting for heat pumps. 
   If the O option is highlighted, select B.
   If the B option is highlighted, select O.
6. To make sure the issue is resolved, test your heating and cooling again.

Please try it and let me know how that goes.

Regards,

Axel.