Fan runs, but the compressor doesn't overnight.

[Jetlife767]

Just replaced our AC system with a heat pump. Everything works as advertised during the day. At night, the blower fan runs all night, the compressor doesn't come on and the temperature never gets below 70. It's early in the season so the outside air temp has been around 70. 

[AxelD]

Hi Jetlife767,

Thanks for posting and sorry to hear about this situation with your thermostat not cooling. No worries, help's here! Could you please share a photo of your wiring? I'd like to see how it's wired. But, let's try to change the O/B wire settings, that might help to fix it:

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 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 these steps and let me know how it goes.

Regards,

Axel. 

[Jetlife767]

Cooling wasn't a problem during the day. The problem only happens during the evening. For some reason the NEST only turns on the fan and doesn't activate the compressor. I have removed the NEST and replaced it with a conventional thermostat to confirm there is no problem with the system. What would cause the NEST to only call for the FAN when the temp set point is as much as 8 degrees from the temp in the house? 

[AxelD]

Hi Jetlife767,

Thanks for replying! Do you mind sharing a photo of your wiring?

Regards,

Axel.

[Jetlife767 · Accepted solution]

I have removed the thermostat, I’m not able to take a picture of the wiring. It was wired correctly and verified by the company that installed the new equipment. We did change from a standard forced air heat/air conditioner to a heat/air conditioner. As noted before, the system was working during the day when the outside temperature was warmer, but from around midnight until around 7 am it would just run the fan and not call for the compressor even when the set temperature and inside temperature were as much as 8 degrees. Is there a setting in the software that would cause this and how do I change it?

[Jetlife767]

That should say our new system is a heat pump.