Hi @adamwright2010,
First I would like to thank you for posting in our community page, on the other hand I apologize for the inconvenience that you are having with your Nest thermostat. Let me tell you some troubleshooting steps that you can try to fix the problem.
It definitely sounds like there's a wiring issue with your Honeywell thermostat.
1. Double-Check the Wiring:
Make sure each wire is connected to the correct terminal on the thermostat:
- Y: Yellow (Cooling)
- W: Blue (Heating - First Stage)
- G: Green (Fan)
- R: Red (Power)
- RC: Red with Jumper (Often combined with R in basic models)
- Y2: Empty (Leave empty for now)
- C: Empty (We'll address this later)
Refer to the official Honeywell thermostat manual or a wiring diagram specific to your model for exact terminal placement. You can find these resources on the Honeywell website or through a web search.
2. Potential Cause: Miswired Cooling (Y) and Heating (W):
Since you're getting heat when calling for cool air, it's likely the Y (cooling) and W (heating) wires are swapped. Carefully switch the positions of the yellow and blue wires on the thermostat terminals.
3. Common Wire (C) - Not Mandatory, But Helpful:
Your current wiring configuration might work without a common wire (C), but it's generally recommended for better performance and stability. Here's why:
- The C wire provides continuous low voltage power to the thermostat, improving battery life (if your model uses batteries) and overall reliability.
4. Do You Need a Common Wire?
If your current setup functions without any issues besides the heating when calling for cool, you might not need a C wire immediately. However, it's still recommended for optimal performance.
Here are your options:
- Option 1 (Recommended): Install a C wire (typically brown or black) from your furnace control board to the C terminal on the thermostat. This will likely require accessing your furnace and may be best suited for a qualified HVAC technician.
- Option 2 (Temporary Fix): If installing a C wire isn't feasible right now, try swapping the Y and W wires as mentioned earlier. This should hopefully resolve the heating during cooling issue.
Important Safety Note: While these troubleshooting steps can help, electrical work, especially near heating systems, can be risky. If you're not comfortable working with electrical wiring, it's best to consult a qualified HVAC technician to ensure safe and proper installation.
If for some reason you have another concern don't hesitate to let us Know.
Regards,
Mario.
