Thermostat is switching from cool to heat when in cooling mode.

[Kalc]

Just recently, my cool/heat system started to pump out hot air when in cool mode. It seems that rather than let the temp rise naturally, the system is switching to heat even though it is on cool mode. I tried to turn off the thermostat and hot air continued to pump out the vents. If I keep the temp low, the air runs but it runs almost continuously. How do I fx this?

[SharonL778]

I seemed to have the same issue.  I replaced a honeywell thermostat with Nest thermostat (not E nor Learning) and matched up all 4 wires (G/Y/OB/R). The system started blowing some cold air initially and then when I increased the temperature to 80 degrees and tried to stop the cooling, the system seemed to start blowing hot air and non stop. I had to cut off the power to the furnace(gas) to stop the heat. Any help would be appreciated.  

[SharonL778]

@Kalc, I just fixed my issue. I changed the setting from O to B wire. The system is working correctly now and stops on its own!  See attached. 

[Kalc]

I just checked and I don’t have that option in the app. Back to the drawing board

[Jenelyn_O]

Hi folks,

Thanks for posting in the Google Nest Community forum. I'd like to know more about it. A few questions: what type of Nest Thermostat do you have? You can visit this link to check what type of thermostat you have. Also, do you see any messages or codes on your thermostat or in the app? 

Please check your thermostat Energy History. It might help you see what your thermostat was doing previously. You can visit this support article on how to check Energy History in the thermostat or in the Nest app.

@SharonL778, I appreciate you for sharing the information that fixed your issue with your thermostat. 

Best,

Jenelyn

[Jenelyn_O]

Hi Kalc,

I just want to check if you managed to see the response above. Please share with us the needed information, as it will help us to move forward.

Thanks,

Jenelyn

[Kalc]

We have the 3rd generation nest. The history said cooling but there was heat coming out of the vent

[Jenelyn_O]

Hey Kalc,

Thanks for checking your Nest Thermostat Energy History. It looks like your thermostat and the Nest app correspond to each other. Could you please share with us your thermostat wiring diagram? Just go to your thermostat Settings > Equipment > Wiring Diagram. 

You can try to call for heat then check if it will reverse your system from heat to cool. Also, please provide your thermostat power readout by going to the Settings then Technical Info. 

Keep me posted.

Regards,

Jenelyn

[Jenelyn_O]

Hi there,

Checking if you still need help. Please let me know, as I'll be willing to assist you further. 

Kind regards,

Jenelyn

[Kalc]

Yellow= Y1 cool

Green = G fan

white = W1 heat

ref= power Rh

power

battery 3.823v

Voc 35.49v

Vi. 7.54v

lin 20 mA(a)

[Jenelyn_O]

Hey Kalc,

Thanks for providing that information. You have a conventional system, and that is the reason why you don't have an option for a heat pump in the app. Also, you have fine power readings for your thermostat, so basically it looks like your thermostat is getting enough power to the wires. Let's take a closer look at it further. Please check if your thermostat has a schedule created. Ensure as well that your thermostat auto schedule is off.

You can follow these guides: 

Manual Schedule

1. Go to your thermostat Quick View menu.
2. Turn the ring and select the calendar icon.
3. Look for any plotted schedule.
4. If you found that there's an automatic schedule created there, reset your thermostat schedule.
   1. Go to Settings.
   2. Look for Reset.
   3. Reset and clear the schedule.

Auto Schedule

1. Go to your thermostat Quick View menu.
2. Go to Settings.
3. Turn the ring and look for Nest Sense.
4. Turn off the Auto Schedule.

Best,

Jenelyn

[EmersonB]

Hi everyone,

I'm dropping by to ensure that everything is covered here. How's it going with your Nest Thermostat? Were you able to perform the steps we're suggesting? We'd be glad to hear from you.

I appreciate the help, Jenelyn.

Regards,

Emerson

[Kalc]

Hello. We did not have any saved schedules 

[Kalc]

The issue has not been resolved. Our cooling switched to heat even though it is set to cool. When I turned off, the heat continued to pour out our vents. Please advise. I am ready to return this nest for another product

[Markjosephp]

Hello everyone,

I know it has been a while, but I wanted to ensure that everything was covered here.

In addition to the discussion, there may be an issue with the changeover valve or with the thermostat settings, and you might need to install a C wire or the Nest Power Connector to help deliver consistent power to the thermostat. Please check if the HVAC system needs maintenance. If your system works for a while but one or more unusual behaviors or previously mentioned issues eventually happen, to test if the issue may reoccur, try running through the following steps:

1. Turn off the HVAC system's power at the breaker switch.
2. Wait for a few minutes, and then turn the power back on.
3. If the issue seems to fix itself but then returns after a short while, the system may need maintenance.

To diagnose possible system maintenance issues, you can install your old thermostat and test the system. This method is useful to determine if there’s a maintenance problem with the system or if the system doesn't provide enough power to the thermostat.

Let us know if you need more help.

Best,
Mark

[ka8]

I am having the same problem. The system worked fine for about a year. We did a factory reset at the direction of Google (I called and had a specialist help me on a different issue) and the thermostat started switching to heat while in cooling mode. This string was not helpful. 

[Markjosephp]

Hello ka8,

I appreciate your time reporting the same issue you're having with your Nest Thermostat. Let's sort this out.

Can you share with me your support ID number? This would help me isolate and look for possible reasons why it triggers your system to switch modes after a reset.

I'll look forward to your response.

Regards,
Mark