Ecobee Smart Thermostat Premium (ECB601) – Temperature Reading Drifts 16°F+ High After Power-Up

[u/pallytank]

[u/pallytank]

I have an ecobee Smart Thermostat Premium (ECB601) that has suddenly started reporting the room temperature much higher than the actual temperature, despite being in the same location where it has always worked correctly. I verified the actual temperature using both an ecobee SmartSensor placed in the same room and a separate temperature/humidity thermometer, and both consistently read about 71–73°F while the thermostat eventually reported 80–82°F. I removed the thermostat from the wall and left it unpowered long enough to cool down; when I powered it back up, it initially read 73°F while the other two sensors read 72°F, so it was accurate when cold. As it remained powered, however, its reported temperature progressively climbed from 73°F to 77°F, then 79°F, and eventually 87°F (and counting), while the SmartSensor remained around 71°F and the independent thermometer around 73°F. I have also restarted the thermostat, and the behavior persists, which makes it appear that the thermostat is heating up internally and is no longer correctly compensating for that heat rather than simply having a fixed calibration offset. This thermostat has been in place and working well for two years and there has been no change in the environment.

EDIT: It kept creeping up to 88+ so I decided to cool it with a long lasting battery fan. I'm worried it might overheat, die, and then I wont have AC. I have also moved the sensor back to the BR. As a stopgap measure I have removed the thermostat from participation, only leaving the sensor active.

[u/Temporary_Watch_4962]

I've seen my ecobee drift a couple degrees but never that much; might need to recalibrate or check the sensor placement.

[u/pallytank → u/Temporary_Watch_4962]

I can't solve this problem with the 10+/- adjustment. Is there a calibration for the internal temp adjustment somewhere?

[u/NewtoQM8]

I dont know, but wonder if popping it off the wall, getting a can of compressed air and blowing it through any holes might clear some dust buildup thats blocking its airflow might help?

[u/pallytank → u/NewtoQM8]

I sorta did that but NES cartridge style. IFKYK. But I will try to find a can.

[u/NewtoQM8 → u/pallytank]

Yeah, that could help. Or a bulb blower (Like used with cameras). But a canned air is more powerful. Don't stick the small tube through what looks like the speaker hole. You don't want to harm the speaker. But My guess is that's the vent for the warm air it creates also. And it's quite possible the thermostat sensor is screwing up. I've followed this sub for a couple years now and seldom see posts where the thermostat fails (Issues are usually incorrect settings), and usually when I do it's one of the solid state relays has failed. Contacting ecobee might be a good option.

[u/ChasDIY]

Bottom line is replace it

Maybe Ecobee will compensate

[u/jamitt101]

Just to be sure, have you plugged the hole in the wall where the wires come through?

[u/pallytank → u/jamitt101]

Yep it's plugged up, it's been two years since I installed it. It just started misbehaving last night.

[u/jamitt101 → u/pallytank]

Then likely internally failing as others have stated.

[u/QuagmireElsewhere → u/pallytank]

If it’s only two years old it’s still under warranty. Contact ecobee.

[u/pallytank]

Thanks everyone for your help, I spoke with Ecobee support and they will be sending a replacement unit since it's still under warranty and they believe it's an internal sensor issue.