Said It Here

Why does my thermostat keep losing power and resetting?

A short in the 24V circuit or a failing HVAC transformer often causes the furnace control board to lose power, which trips the 3-amp safety device and kills the thermostat. This leaves the system completely dead or causes smart thermostats like the Nest and Ecobee to repeatedly reboot during a call for heat.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Resetting the 3AMP device/fuse
  2. 2
    Removing wires one at a time to check for shorts
  3. 3
    Inspecting outdoor unit low voltage wires for damage
  4. 4
    Planning to call a professional service technician
  5. 5
    checking furnace error blink codes
  6. 6
    changing air filters
  7. 7
    inspecting limit switches and flame sensors

In their words

Unedited, most upvoted first, each linked to the thread it came from.

“My Nest thermostat was showing an E298 error, and after digging a bit it I found that the furnace/control panel doesnt have any lights or power.”source ↗

“The outside AC unit is also not running.”source ↗

“After that, I pressed the gray button next to it as it’s the safety reset apparently? It flipped the 3AMP switch up and I could hear a slight hum.”source ↗

“At this point I’m trying to determine whether the problem is simply the NOARK 3A device, or whether there could be another underlying issue such as the HVAC transformer, control board, power supply, or a short in the 24V circuit.”source ↗

Icy_Moment_8783 · r/hvacadvice · 1 upvotes

“Thermostat is an ecobee, it seems to run the furnace for about 5-10 minutes then will restart. Screen goes black for about 2 minutes while the furnace keeps calling for heat.”source ↗

IJustLoveDoggosOkay · r/hvacadvice · 1 upvotes

“My Ecobee reboots anytime my furnace faults , the four flashing lights will tell you what the fault is !”source ↗

Bendover197 · r/hvacadvice · 1 upvotes

Where this came up

r/hvacadviceelectricalfurnacehvacthermostattroubleshooting

People with this problem also raised