(2) Nest thermostats on (2) furnaces but one blowing cold air

[Palyn11]

I have 2 furnaces and 2 nest thermostats wired exactly same but my upstairs unit only blows cold.

[zoeuvre]

Hi Palyn11, 

Uh-oh! I'm sorry to hear that your upstairs thermostat only blows cold. Let me take a look at this for you. A few questions: 

1. Are you located in North America or Europe? 
2. What type of Nest Thermostat do you have? 
3. Is the Nest thermostat newly installed?
4. Did you used the Compatibility Checker tool to confirm the thermostat's compatibility. 
5. Does the thermostat screen indicate that it’s actively calling for heating? 
6. What type of furnace do you have? (gas, electric, etc.)
7. When did heating last work? 
8. Did heating ever work with the Nest thermostat? 
9. Did the heating work with the previous thermostat? 
10. Did you turn off the power to the HVAC system? 
11. Did you recently turn off any breakers?
12. Have you recently experienced a brownout or blackout? 
13. Is there a light switch near the heater that controls an outlet? 
14. Did you select the correct fuel type? 
15. Do the LED lights blink on the HVAC control board? If yes, locate the light. 
16. When was the last time you changed the furnace's air filter? 
17. Have you experienced extremely cold weather lately?
18. Is this the first notable temperature drop of the year in the area?

Keep us posted. We're happy to help.

Best,

Zoe

[Palyn11]

1. North America 

2. Basic programmable 

3. No. It’s been a few months

4.  No. I didn’t but I know it’s compatible 

5.  Yes. It says it’s heating

6. Gas furnace

7.  Before I change them both out.

8. I have (2) thermostats as mentioned and 2 systems. 1 upstairs and 1 downstairs. The downstairs works. 
9. Yes.

10. Only when o installed it. It’s on. Air blew fine last summer.

11. No.

12. No.

13. Yes. But it’s on. 
14. Yes

15. I don’t have LED lights on HVAC control board 

16. last month 

17.  No.

[zoeuvre]

Hi there, 

Thanks for getting back to us, and I'm sorry for the late response. Does your thermostat has C wire connected to its base? And could you gather the power readouts of VIN, IIN, and PS-* under Settings > Equipment > Power Info? 

Regards,

Zoe