cancel
Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for 
Search instead for 
Did you mean: 
Help
Replies are disabled for this topic. Start a new one or visit our Help Center.

Nest learning thermostat runs gas forced air furnace when in AC mode, wiring, C wire are all correct

Jeff32
Community Member

‎09-06-2023 07:08 AM

Furnace comes on and runs continuously until power is cycled.  This happens in AC mode, and sometimes while the AC is also running. All wiring has been double checked, C wire is in place and connected properly. I had the newer and cheaper Nest thermostat which worked fine for a year, but then upgraded to the learning thermostat to utilize a remote wireless sensor. I think it is a bad thermostat, it's about 2 months old, how do I get a replacement ?

0 Kudos
Reply
3 REPLIES 3

zoeuvre
Community Specialist
Community Specialist

‎09-08-2023 11:28 AM

Hi Jeff32, 

 

Thanks for reaching out to us, and I'm sorry to hear about the situation. I want to check if you are still in need of any help.

 

A few questions: where are you located? From North America or Europe? What type of Nest Thermostat do you have? If you have the Nest Learning Thermostat or the Nest Thermostat E, go to Settings > Tech Info > Power and gather its Battery, VOC, VIN, and lIN. If you have the Nest Thermostat 2020, go to Settings > Equipment > Power Info to gather its VIN, IIN, and PS-*. 

 

Also, check your air filter, as a clogged filter might cause a similar symptom. If the air filter is dirty and needs to be changed, replace the filter and let us know if the situation continues after you change it. Refer to the Air filters and filter reminders article for more details. 

 

I'll look forward to your response. 

 

Best,

Zoe 

0 Kudos
Reply

Jeff32
Community Member
In response to zoeuvre

‎09-09-2023 05:12 PM

Hi, and thanks for responding. I am located in Buffalo, NY, USA. It is a Nest Learning thermostat. The voltages you asked for run in a range, Battery 3.914-3.928 V, Voc 35.12-37.59, Vin 35.12-37.59, Iin 200ma. The furnace transformer is putting out 28.4 volts AC. Air filter is clean.

0 Kudos
Reply

zoeuvre
Community Specialist
Community Specialist
In response to Jeff32

‎09-10-2023 10:51 AM - edited ‎09-17-2023 11:13 AM

Hi there, 

 

Thanks for getting back to us. Let's try these steps:

 

  1. Turn off the power to the HVAC system.
  2. Remove the thermostat display.
  3. Remove the wire from the C terminal. Cover its metallic part with electrical tape or a wire cap, and tuck it into the wall.
  4. Reinstall the display and press it until it clicks into place.
  5. Turn the power back on.
  6. To verify if the situation is resolved, check if the system no longer power cycle.

 

Also, you may reinstall your old thermostat if you still have it just for us to isolate if your Nest Thermostat or the system itself cause the situation. 

 

Let us know how it goes.

 

Regards,

Zoe  

0 Kudos
Reply