On Saturday, February 25, 2017 at 7:21:14 AM UTC-8, trader_4 wrote:
On Saturday, February 25, 2017 at 10:14:05 AM UTC-5, Sheelman73 wrote:
My furnace was acting fine until one day about 2 weeks ago. What happens is
that the burner turns n as usual and heats up for about 10-15 minutes. Then
the flame shuts off and the blower continues to run (blowing cold air) until I
shut of off by the switch in the side. The metal box around the burner is too
hot to touch. Could it be overheating for some reason. In order to start it
back up, I have to push the reset switch and turn the switch back on. Then the
issue occurs again. So far I have had the unit tuned up and the burner was
changed out. Any siggesti Ha?

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Sounds like the fan limit switch is out of adjustment or gone
bad. It's supposed to stop the fan when the plenum temp drops
below the set point. That's assuming it's an old furnace
without modern electronic controls. And if it is, if you're
anywhere that needs heat even a modest amount of time, it's
probably terribly inefficient. If it's a modern furnace, then
I think they are done based on time now, not temp.

Replacing the fan limit switch worked for me but I ended up
getting a new furnace.