Nest is blowing hot air on cold mode

[mikevech]

• Please help, my best thermostat is blowing hot air on cold. It was already installed when I got the house. I replaced the thermostat last (left the wires as it was) and it helped for a while and now no matter how many times I reset the nest thermostat is it not cooling the house 

[jenniffert]

Hi @mikevech,

Thanks for reaching out here in the community! I'm sorry to hear your Nest thermostat is blowing hot air instead of cool air. Help is here!

To better assist you, I'd like to ask a few questions:

• What model is your Nest thermostat?
• What type of HVAC system do you have?
• Did you perform a restart or factory reset (all settings) on the device?
• When was the last maintenance check for your HVAC system?
• Does the issue happen only with heating, only with cooling, or with both?
• Would you mind sharing a photo of the wiring installation?

Please keep me posted.

Best regards,

Jenniffer

[mikevech]

• What model is your Nest thermostat? (3rd gen nest thermostat)
• What type of HVAC system do you have? (electric, single fuel, forced air)
• Did you perform a restart or factory reset (all settings) on the device? (multiple times)
• When was the last maintenance check for your HVAC system? (twice a year)
• Does the issue happen only with heating, only with cooling, or with both? (only cooling)
• Would you mind sharing a photo of the wiring installation? (please provide instructions on how can I share photos to this forum)

Please keep me posted.

[jenniffert]

Hi @mikevech,

Thanks for following up and for all the information. Let's try to fix this!

To attach a photo here in the community thread, look for the camera icon in the reply box where you type your message. It says 'Insert photos' and you will be able to select the files.

To troubleshoot why your Nest thermostat might be blowing hot air instead of cool air, I'd suggest the following:

• Check the energy history in the Nest app. This can help explain why your thermostat unexpectedly turned on or off, or why the temperature changed. Here's the helpful article: How to Check Your Energy History.
• Before checking the wires, turn off the power to your HVAC system at the breaker box. Verify that the wires are securely connected to the terminals and the connector buttons are fully pressed down on your Nest thermostat.
• Observe if your Nest thermostat screen turns orange when you want heating or blue when you want cooling. This can help identify if the Nest thermostat is able to receive the instructions to change the temperature and diagnose if the inconvenience is related to the thermostat or the HVAC system. 
• If there's a wire in the C connector, check its connection to your system or thermostat. A missing C wire can limit power and affect cooling. Be sure to turn off power to your home at the breaker, fuse box, or system switch to protect yourself and help prevent damage to your system. If there isn't a wire in the C connector, you can install a C wire or Nest power connector. This can help the thermostat provide more power to turn on the system and help regulate heat. For more information, you can refer to the next article: Troubleshoot strange heating or cooling behavior.

Let me know how it goes.  

Best regards,

Jenniffer

[mikevech]

humidifier is removed completely so not sure if I have an extra wires or not

[jenniffert]

Hi @mikevech,

Thanks for reaching out to the community and for the photo! I apologize for the delay.

I noticed a wire connected to the asterisk (*) terminal on your Nest thermostat, which is commonly used for humidifiers. Here's what you can do:

1. For your safety, turn off the power to your HVAC system at the breaker box before removing any wires.
2. Remove the wire currently connected to the asterisk (*) terminal.
3. Ensure the buttons on the side of the thermostat terminals are firmly pressed down.
4. Turn the power back on to your HVAC system at the breaker box.

Check if the system is set to single fuel or dual fuel:

• On your thermostat, go to Settings > Equipment.
  • If the W1 label says Alt on the equipment screen, the HVAC system is on dual fuel. If it says Aux, the system is set to single fuel.
• If your system isn't set up correctly, select Continue > Continue > Pro Setup > Continue > Single Fuel or Dual Fuel > Exit Pro Setup.

Now, let's adjust the heat pump orientation settings:

• On your thermostat, go to Settings.
• Select Equipment.
• Select Continue > Continue.
• Select Heat Pump.
• 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.
• To make sure the issue is resolved, test your heating and cooling again.

For more information, you can check out the next article: Troubleshoot heat pump issues.

Please keep me posted.

Best regards,

Jenniffer