Is your Nest thermostat heating your home when you want it to cool instead? This problem happens sometimes. The good news is you can likely fix it. 

But, Why is my Google Nest heating instead of cooling? Well, a variety of reasons I must say. In general, wrong pump heat pump settings, old-fashioned heating systems, and wrong wiring cause this. But there are some other issues as well. There are some DIY fixes to resolve these issues.

To know how to deal with the problem, keep going on with me. I’ll guide you through the potential causes and how to resolve each of the issues. 

5 Reasons Why Your Nest May Be Heating Instead of Cooling

I’ve listed 5 of the most likely reasons your Nest thermostat runs heat instead of activating your home’s air conditioning. By methodically checking each, you can get to the root cause and get your system running properly again.

1. Check Thermostat Settings

The simplest mistakes can lead to the biggest headaches. Confirm that:

• Cooling mode is specifically enabled on your thermostat
• The setpoint temperature displayed is lower than the current room temperature.

How to Fix?

1. Turn the outer dial on the thermostat to switch the system into Cool mode (you may see a snowflake icon).
2. Next, turn the dial further counter-clockwise to lower the setpoint temperature below the stated room temperature.
3. Check that the fan is set to either On or Auto.
4. With cooling now activated, monitor operation over the next few hours to observe normal functioning.

2. No Central AC Unit Installed

Nest thermostats require a cooling system to control summertime cooling. If your home only has a gas furnace or electric heating without central air conditioning, the Nest will fail to trigger cooling – leading to continued heating operation.

How to Fix?

1. Confirm if your home utilizes forced-air ductwork, hydronic baseboards, or another distribution approach.
2. Determine if an air conditioning unit & outdoor condenser is currently present.
3. If no cooling equipment exists, hire an HVAC company to install central air conditioning.
4. With a compatible cooling system now enabled, reconnect Nest to control both heating & AC.

3. Incorrect O/B Reversing Valve Setting

Heat pumps require a special setup of the O/B orientation, which handles switching between heating & cooling modes. If reversed from your specific unit’s needs, warm air will blow from vents when set to cool.

How to Fix?

1. Go into Menu » Equipment » Heat Pump » O/B Orientation on your Nest.
2. Locate wire labels on your HVAC equipment itself for reference.
3. Set Nest’s O/B setting to align with wiring – choosing either O or B.
4. Run System Test to validate heating & cooling alternate correctly.

4. Stuck Reversing Valve

With heat pumps, a component called a reversing valve physically shifts modes from heating to cooling. If mechanically stuck, this can lead to heating activation when cooling is desired based on Nest settings.

How to Fix?

1. Set the Nest into cooling mode and feel air flow from vents over a 5-minute trial.
2. Contact an HVAC technician to inspect the heat pump operation.
3. Request testing & repair of the reversing valve if found to not shift modes.
4. Confirm normal functionality after repairs are made to valve operation.

5. Wrong Control Wiring

Finally, simple wiring mistakes or loose connections can lead to the thermostat signaling heating incorrectly when cooling is expected. This applies to both conventional and heat pump systems.

How to Fix?

1. Shut off power to the HVAC system at the breaker panel.
2. Pop off the Nest plate & check wires are inserted fully & in the correct ports.
3. Refer to equipment wiring diagrams if heat pump; or typical A/C wiring otherwise.
4. For 2-stage systems, verify both stage 1 & 2 compressor ports are wired.
5. Restore power & perform several heating & cooling test cycles.

Hopefully going through this structured troubleshooting isolates why your Nest is stuck on heating. Applying the appropriate solution steps will then resolve the problem for good.

General Guieline: How Can You Fix the Nest Thermostat Not Cooling Issue?

If your Nest still isn’t cooling properly, here are some troubleshooting tips:

Confirm The Type Of Cooling System

Determine if you have a heat pump, conventional A/C, evaporative cooler, etc. Proper wiring depends on which system you have.

Check The Nest Thermostat Wiring

Inspect wiring connections to ensure cables are securely inserted into the proper terminals.

Disconnect The Common Wires

Unplugging the C wire and turning the Nest on and off can reset incorrect system signals.

Check The Circuit Breaker Box Thoroughly

Make sure the breaker powering the A/C unit and air handler is switched fully on. Also, check for tripped fuse issues.

Auto-Schedule Might Be Unable

Review auto-schedules to confirm desired temperatures for the current time of day. Adjust schedules if needed.

Check The RC / RH Wiring Functions

Make sure either RC or RH has 24V power, not both. In rare cases, they can conflict.

A Blown Fuse Might Be Causing The Issue

Inspect the indoor HVAC unit for any blown fuses interfering with operation.

Incompatible Nest Device

Older systems may have compatibility issues. Consider replacing it with a newer model Nest.

Make Sure Of An Updated Nest Software

Update to the latest software in case a bug fix has been released. Perform reset after updating.

How Can You Factory Reset Your Nest Thermostat? A Step-By-Step Approach

Is your Nest acting up and not responding to adjustments? Before replacing the unit, try restoring the factory default settings first. Resetting can clear up problems caused by configuration errors or software issues.

Here is a simple process to reset your thermostat:

1. Step 1: Press down on the outer ring to open the Quick View menu
2. Step 2: Turn the ring and select Settings
3. Step 3: Choose the Reset option
4. Step 4: Confirm resetting All Settings when prompted
5. Step 5: Agree to erase all customizations
6. Step 6: Press the ring again to confirm and restart

An alternative is to reset by power cycling the hardware.

• Option 1: Press straight down on the thermostat until the screen shuts off
• Option 2: Release button and short press ring to turn back on
• Option 3: Remove batteries from battery compartment
• Option 4: Reinsert batteries to reboot system

Resetting your Nest often helps troubleshoot heating and cooling problems. I recommend trying a reset before replacing the thermostat itself. This can revive normal functioning without the hassle and expense of a new thermostat.

Recommended articles:

• Can I Use a 370V Capacitor Instead Of a 440V Capacitor
• Can I Use a 440V Capacitor Instead of 250V

In Summary

Troubleshooting why your Nest is stuck improperly heating when cooling is the goal can be tedious. But walking through common causes like 

• Misconfigurations 
• Wiring issues, 
• Faulty valves  
• Inadequate cooling equipment 

All these will help zone in on the problem. 

Applying the solutions outlined can restore your smart thermostat to properly activate heating or air conditioning. Anyway, if nothing works, factory resetting might revive normal functionality.Reach out to a professional HVAC technician for additional support if problems persist.