I have a Trane XR90 gas furnace that is about 5 years old and a honeywell 5/2 programmable thermostat, same age (sorry, don't have model #). When thermostat is set to eitherh heat or cool and temperature is raised or lowered beyond room temp, the furnace will not kick on (neither the temp nor the fan). Switching the thermostat's fan switch to "on" does not turn the blower on either. Trane diagnostic light is blinking continuously, seemingly slow ("no call for heat"), though I can't say for sure, because I've never seen it when it was blinking fast. I swapped out the thermostat for a new one and no change. Breaker has been checked. Batteries in thermostat checked. Any ideas about what is going on would be much appreciated.

Thanks.

Check the thermostat wire connections at the furnace control board. If system is equipped with a condensate pump and the secondary switch is wired in, check pump reservoir for over-filling.

Check the thermostat wire connections at the furnace control board. If system is equipped with a condensate pump and the secondary switch is wired in, check pump reservoir for over-filling.


Thanks, I will give that a try.