Goodman GMNT Condensing Gas Furnace not reaching Set Point Temp

[briegg]

2002 8 yr old unit with Honeywell Chronotherm IV Plus Thermostat.  Thermostat settings are 71 wake, 66 leave, 71 return, 66 sleep.  Will wake up to 60 degree temperature.  Unit will come on, but only for a bit, and will not reach 71 until 7pm, after the return setting.  When unit comes on, it's like the gas dryer where it will start, and then the flame will light sending heat.  Changed the air filter today and now temperature will not even reach 66 even at night.  Please advise.

[RegUS_PatOff]

has it worked OK earlier this winter ?

have you recently installed this Thermostat  ?  Will it work OK with the "old" one ?

 

 

 

 

[briegg]

Worked fine all winter, just went down the past week. Thermostat has been here since we moved in in March, don't know where the old one is. Woke up today to 70 degrees when it kicked on at 7am and ran for an hour. Now at 8:05 it's back down to 68

[RegUS_PatOff]

If you could check for 24vAC between the Themostat Connections:

®ed and ©ommon

®ed and (W)hite

here's the T8601D Chronotherm® IV Deluxe Programmable Thermostat instruction manual

[ACtechGUY]

My advice is , get rid of the Chronotherm!!!!! The whole Chronotherm series have a way of malfunctioning in the most unpredictable ways. Try a new thermostat and see if your problem does not improve. (As a test you can remove the stat from the subbase and jump from W to R . IF HOUSE HEATS UP , THEN THERMOSTAT BAD!!)

[briegg]

Root cause was a dirty Flame Sensor.  Cleaned it off and worked like new.