Hello @rettajo1,
Thanks for reaching out to the communit. I'm truly sorry to hear you're receiving E73 error code on the Nest thermostat. I'm happy to help you.
To gather more information, please answer the following questions:
- What HVAC system do you have?
- When did the inconvenience start?
- What's the current wiring configuration?
- Have you had any power outage?
In the meantime, please follow these troubleshooting steps:
- Wires must be firmly connected to the terminals. Ensure at least ¼ to ½ inch of the copper wire is exposed, straight, and inserted fully into the correct connectors. If needed, strip and reinsert the wires. If necessary, Strip and re-insert the wires
- Wires that are too thin (smaller than 18 gauge) won't work with the Nest Thermostat. A Nest Pro or local technician can replace them if necessary.
- The Nest Thermostat needs 18 to 22 gauge solid-core copper wires. Stranded wires are incompatible. If you have stranded wires, a Nest Pro or local technician can replace them.
- Note: If you feel comfortable, please check the voltage of the RH wire using a voltmeter. The normal readout should be somewhere between 20 and 30 V (24 V is most common).
- Check the Air filter on the HVAC system.
Please, keep me posted!
Best regards,
Eitan
