Hello @BobbyKun,
Thank you for posting in the community. I'm sorry to hear that you're experiencing the E72 error with your Google Nest Thermostat, especially given that your PTAC unit appears to be running despite the error message. I understand this can be quite puzzling, and I appreciate you providing these specific troubleshooting steps from Google. I'm here to help you go through them to try and resolve this.
Based on the information you've shared, the E72 error indicates that your thermostat isn't detecting proper power to a wire or can't detect the wires at all. Let's follow these steps exactly as outlined to check your system's power and wiring, as this is often key to resolving power-related issues.
Here are the steps to follow:
1. Check the system power.
- First, we need to ensure that the power to your PTAC system is fully on.
- Locate the power switch for your system. This is usually found in your breaker box or fuse box. In some homes, it might look like a regular light switch located near your PTAC unit.
- Confirm that the power is definitely on. Some systems might have a single switch, while others might have two separate switches, one for heating and one for cooling. Make sure both are in the "on" position if applicable.
- After you have checked and confirmed the power is on, go back to your Nest Thermostat and see if it is now working correctly.
2. Check the thermostat wires.
Important: To protect both yourself and your Nest Thermostat, you must turn off the power to your system and thermostat at the breaker or fuse box before you touch or adjust any wiring.
- Once the power is off, gently pull off the Nest Thermostat display from its base.
- Now, carefully check that the wires are inserted correctly into the thermostat's connectors on the base plate. Make sure that each wire is fully pushed into its connector and that every connector with a wire is securely pressed down.
- Also, check that approximately 6 mm (or ⅜ inch) of exposed wire is visible for each connection. This ensures good contact.
- Once you've confirmed the wires are properly seated, turn the power to your system back on at the breaker or fuse box.
- Go back to your thermostat and check to see if it is now working as expected.
If you have completed all these troubleshooting steps and your thermostat is still not working correctly, the next step would be to contact a local professional for further assistance, as they can perform more in-depth diagnostics on your system's wiring and power supply.
Please let me know how it goes after you've tried these steps.
Regards,
Kevin
