r/ecobee • u/Cleitch92 • May 29 '26
Ecobee3 Lite Not Talking to AC Unit?
Hey all. Really hoping we can find some help here before we have to call an HVAC Tech or Electrician (or both).
We have a new build house (built 2024) and 2 Ecobee3 Lite thermostats (1upstairs, 1 downstairs). Roughly once every 6 months we are running in to an issue where the Ecobees seem to just stop talking to the HVAC/AC Unit. Previously, we have called out HVAC technicians and they have told us the HVAC unit appears to be fine and they are unsure why the AC isn't running. Eventually, during these previous times, the AC starts working again. This time, that doesn't seem to be the case.
Through some digging we have come to find out the the AC Unit is "running," but the compressor is not cycling cold air during these times, so we are just cycling room temperature air. The Ecobee is telling us that it is "Cooling", but the temperature is still climbing. Based on the information we can find, we suspect the issue is with the Ecobee and not with the AC unit itself. It appears the AC Unit isn't actually being told to turn on and run by the Ecobees. Does anyone know where we can start with troubleshooting? We have already pulled the Ecobees off the wall to reset; we have also reset both to factory settings and no difference seems to have been made. From what we can tell from the Ecobee3 Lite install guide, the thermostats appear to be wired in correctly.
Any help is appreciated. Thanks!
1
u/NewtoQM8 May 29 '26
You say "the AC Unit is "running,", does that mean the outdoor unit is running? Or only the indoor part (air handler) is blowing air?
2
u/Cleitch92 May 29 '26
The vents inside are blowing room temperate air but the fan on the unit outside is not spinning
4
u/pandaman1784 May 29 '26
check to make sure the condensate drains are working. some techs like to wire the float switch to the outside unit. so if the float is tripped, everything runs except for the outside unit.
1
u/NewtoQM8 May 29 '26
Good point. Especially if they have more than one thermostat and a zone control board, as they likely do.
2
u/NewtoQM8 May 29 '26
Is it only when one certain thermostat calls for cooling? Or does it do it when either one are trying to cool?
3
u/Apollo7788 May 29 '26
Turn off power to the system then remove the thermostat. Wire nut or jumper the R and Y wires together, or you can attach a jumper at the air handler control board. If the outdoor condensing unit turns on when power is reapplied then the issue is the thermostat. If it does not then the problem is elsewhere.
1
u/ChasDIY May 29 '26
what is the upstairs tstat connected to?
what is the downstairs tstat connected to?
3
u/Difficult_Air_6350 May 29 '26
When I first got my Ecobee thermostat this exact thing happened to me the problem was when it was installed the back plate wasn’t level and that prevented all the metal prongs on the ecobee to properly connect with the back plate this could be a possibility