HVAC Air Conditioner, fan not turning on or weak

[mike77fz]

Hi,

I recently swapped the basic programmable thermostat that the HVAC installers setup with a Google Nest Thermostat, model GA01334-US

Our HVAC unit is for cooling only. It seems that the Nest is trying to be more power efficient by keeping the air handler fan speed very low or off completely.

The set temperature is not being achieived, I think the Nest is thinking that it doesn't need to turn on the air handler fan. In the Google home app, I've been manually setting the fan timer to stay on for 8 hours.

The AC compressor is outside with the air handler inside mounted to the warehouse ceiling. The thermostat is located in our office area and is set to 66 or 70 degrees however the inside temp never gets below 80 or so. Per the install instructions I found, the Y2 wire should be connected to the O/B connection of the Nest.  The rest of the connections were straight forward. How can I force the Nest to turn on the fan to full speed as well as get it to cool down. I understand it's hot outside, however the AC compressor and air handler are massive and don't understand how it is not able to cool down the space.  It seemed to work better with the original thermostat.  Any suggestions? Going to switch back to the original thermostat to see if there is any difference. 

We do turn the system off every night via Google automations and turn it on the same way.

Thank you,

Mike

[chaconmorales]

Hi @mike77fz,

Thanks for reaching out to the Community. I am sorry that you are having issues with your Thermostat features for fan control, I’d be happy to help you. Let’s check it out.

Before we get started with further troubleshooting, let me ask you some questions

1. What Nest Thermostat model do you have?
2. Does the thermostat display show any error codes or messages?
3. Are you able to share a picture of your wiring?
4. Let me know if you did change back to the original thermostat and if you encountered any differences.

Here are some steps you can try to troubleshoot the issue:

Basic Checks:

• Power: Ensure your AC unit is turned on and receiving power. Check the circuit breaker or fuse box to see if a tripped breaker or blown fuse is interrupting power supply.
• Thermostat: Verify that your thermostat is set to "cool" mode and the desired cooling temperature is lower than the current room temperature. A thermostat set to "heat" or with a temperature set higher than the room temperature won't trigger the AC fan to turn on.
• Air Filter: A clogged air filter can restrict airflow and put strain on the system, potentially causing the fan to malfunction. Check your air filter and replace it if dirty. Please review this guide for further details related to Fan control with a Nest thermostat.

You can also check the following article to verify your Nest thermostat compatibility, based on the wiring details you have provided.

Please keep me posted. 

Best regards,

Mario