Wiring help - Furnace & AC both running

[Fishslippers17]

My furnace and AC are running at the same time. I have tried troubleshooting multiple different ways but can't seem to sort it out.

On my old Honeywell thermostat W2 had a black wire jumper going into an unmarked receptacle that also had a white wire.

I can't seem to post a picture on here. I'll try to add one after this post. Any help is appreciated. This is driving me nuts! 😄

[Fishslippers17]

Picture of old Honeywell wiring 

[Markjosephp]

Hello Fishslippers17,

Thanks for reaching out here in the Google Nest Community Forum. I'd be happy to take a look at this for you.

I have a few questions to ask to make sure your Nest Thermostat's configuration is correct:

• Which type of Nest Thermostat do you have?
• When did the issue start?
• What other strange symptoms have you experienced since the problem started?
• Are there any report messages? If so, what are they exactly?
• Is this a new installation?
• What kind of HVAC system do you have? (Heat pump, conventional system, etc.)
• When was the last maintenance check for your HVAC system?
• Have there been any recent changes or upgrades to your HVAC system?
• Gather the power readings in the Technical Info settings.

I'll look forward to your response.

Regards,
Mark

[Fishslippers17]

Hi Mark, Thanks for reaching out.

- Nest Learning Thermostat

- Issues started immediately after installing nest. I have tried multiple different wiring configs and trouble shooting.

- No messages, new install.

- Conventional system, checked February 2023

- No recent upgrades to system

[zoeuvre]

Hi folks,

@Fishslippers17, thanks for the follow-up. Could you also send us a photo of how you connected your thermostat wires to the Nest Learning Thermostat base? It should be wired as shown below, based on your previous thermostat wiring configuration.

I appreciate your help, Mark.

Best,

Zoe

[Fishslippers17]

Thanks Zoe,

I tried this but my AC fan is still spinning with my furnace is blowing hot air. I have heard that this is the wiring to set up a heat pump, but I have a separate furnace and AC unit.

[Markjosephp]

Hello again,

Way to go, Zoe!

Great troubleshooting so far! Thanks for giving it a shot, @Fishslippers17.  To sum up, after making changes to the wiring diagram shared above, were you able to change your thermostat's settings as well? If you haven't yet, try to press and hold the screen or button for 10 seconds until it shuts down. This would refresh it and make sure to confirm the wiring changes appear on the screen. Then, if the same issue persists, follow these steps:

1. On your thermostat, go to the Settings/Nest settings icon.
2. Select Equipment.
3. Select Continue, and then Continue.
4. Select the Heat pump.
5. The Nest thermostat defaults to an O setting for heat pumps.
   1. If the O option is highlighted, select B.
   2. If the B option is highlighted, select O.
6. To make sure that the issue is resolved, test your heating and cooling again.

Keep us posted.

Regards,
Mark

[Fishslippers17]

Thanks for the tips!

I tried doing the reset and it seemed to keep the AC off more often... But it's definitely still running while I'm trying to heat the house with the furnace.

I then went through the equipment settings and changed from option o to option b and the AC seem to really take over and the house started getting cold.

I'm kind of at my wits end with this. I've tried so many different things. I don't have a heat pump so why would I have the heat pump setting on?

[Markjosephp]

Hey there,

Thanks for keeping us in the loop. Based on your old thermostat wiring diagram, you have a heat pump system with an O/B terminal. To ensure you get the correct configuration, can you share with us your HVAC system make and model? Also, it would be better if you could also share with us a photo of its control panel showing how the wires are being labeled.

Best,
Mark