Furnace doesn't heat house to desired temp?

[reznunt]

- PAYNE Model PG8JAA/MAA Furnace (electronic control board)
- BLOWER WORKS
- GAS WORKS.

Problem: The house will not warm up to the desired thermostat-set temperature.

FIRST CYCLE - Once thermostat is set to "heat", the gas turns on and heats element for about 20 seconds and shuts off. Blower starts and blows slightly warm air (not hot) and continues to run until cold air is blowing from vents. The blower then shuts off.

SECOND CYCLE (a few seconds after first cycle)- The gas DOES NOT turn on to reheat the heating element. Instead, the blower starts up again and blows cold air. This cycle is repeated and the gas never turns back on.

Note: After a few cycles, if the thermostat is set to "off" and left alone for a lengthy amount of time, the system goes through the first cycle by setting thermostat to "heat" again. If the thermostat is set to "off" and is then set to "heat" immediately, the second cycle repeats itself.

Any ideas before I call the pros?

 

[HoosierBuddy]

Sounds like the furnace is shutting off the burner on high limit.

Phil

 

[lametec]

It shouldn't hit the high limit after 20 seconds.

Sounds more like flame sensor isn't detecting a flame.

The diagnostic light on the controller might be blinking. If it is, count the number of short and long blinks. Short flashes is the first digit, long flashes are the second digit. (i.e., 2 short and 3 long is code 23).

Check the last couple pages in this pdf for the troubleshooting guide: http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/im-pg8j-11.pdf

 

[D KRAGER]

Gas supply problem? Are you sure you have the proper gas pressure?

Just thinking out-loud.

 

[trailwart]

i just had the same issue on mine. took panel off and noticed my lights were flashing code, ended up as the flame sensor.
cleaned sensor and been fine ever since. common problem. what does your diagnostic lights do right now??

 

[Rosco]

If not the sensor, could the vent be clogged?

 

[reznunt]

It shouldn't hit the high limit after 20 seconds.

Sounds more like flame sensor isn't detecting a flame.

The diagnostic light on the controller might be blinking. If it is, count the number of short and long blinks. Short flashes is the first digit, long flashes are the second digit. (i.e., 2 short and 3 long is code 23).

Check the last couple pages in this pdf for the troubleshooting guide: http://www.xpedio.carrier.com/idc/groups/public/documents/techlit/im-pg8j-11.pdf

i already checked the diagnostic led. it blinks code 12 which is "normal operation" according to the manual.

 

[reznunt]

we found the problem. apparently, when i went to change the dying AA batteries in the LCD touchscreen thermostat, it popped a 3A fuse. i didn't know unplugging the thermostat and plugging it back in would do that.

but thanks for all of the input!

 

[ddawg16]

I love a happy ending....