E298 error after thermostat has been running for months

[RobI1]

I have been using this thermostat for a few month and all of a sudden I am getting an E298 error message. After a while, the error magically clears and the system runs again. Then a little later I get the message again. It cannot be the wiring as it has been running properly for months. Has anyone else had this happen? I think the thermostat may be defective. 

[David_K]

Google has good guidance on how to troubleshoot this:

Troubleshoot a "No power" alert on the Nest Thermostat (E298 or M20 help code) - Google Nest Help

[RobI1]

It is not a wiring issue. The thermostat has been working without issue for 3 months. Last night, it showed the E298 message 4 times. After about 30 mins the message disappeared and the system ran as it has for several months. It is not a fuse, filter or any other problem with the actual system. 

[gmelanymelissa]

Hi @RobI1, 

Thanks for posting here in the community. I'm sorry to hear that your Nest thermostat got an E298 error message. Help's here!

To better understand the situation, I'd like to ask a few questions:

• What type of heating, ventilation, and air conditioning (HVAC) system do you have?
• Is this a new installation?
• What kind of HVAC system do you have?
• When was the last maintenance check for your HVAC system?
• Do you mind sharing a picture of the wiring installation?
• Is the display working properly?
  • If so, could you please check the battery level, on your thermostat, open the Menu view and select Settings > Battery. The icon changes depending on the charge level.
• Have you used the AC recently?
  • If you have been using the AC recently, please check if the air filter is clogged or dirty. A good airflow is necessary for the thermostat and your HVAC system to work properly.

In the meantime, let's check a few things:

• Check if the emergency switch is on. This isn’t the same as the breakers on the fuse box. It’s a breaker right next to the furnace or boiler and might be a light switch, breaker, or T switch.
• If you have a voltmeter, you can check if the wires are receiving the proper voltage.
• Check if there isn't an undetected wire like C or R wire. This means that the wire is not sending voltage to your thermostat. Follow these steps to Check the wiring.

@David_K thanks for your help, that's a great resource for everyone!

Keep me posted.

Best regards, 

Melany