My 8 yr. old Comfortmaker will turn on, burner will light, then will occasionally shut down 10 minutes later, even tho the temp is not up to the correct temp. Burner goes out, fan stays on, blows cold air. I can turn off the unit at power switch, then when I turn on the burner will light, sometimes staying on and other times going off after 15 minutes. Why?
Why does the gas furnace heat up and then blow cold air
heating
Best Answer
Sound like this may be the same problem as described on Why does my furnace need frequent power resets?
You didn't mention if the furnace comes back on on its own or not. If it doesn't (or doesn't as often as it should), it sounds like the exact same problem I posted about in the above link: a dirty flame sensor. If this is the case, cleaning it will probably make the problem go away.
If the furnace is coming back on on its own, then:
Checking the sensors is probably easiest.