furnace

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I would suggest that you check the fan limit switch, and the fan rheostat. the reason the furnace is shutting, the high limit on the furnace is kicking off burner, because the fan limit is not kicking in moving the heated air from the furnace chamber. turn your thermostat on wall to manual, and see if fan runs only without furnace burning. If so, i would look at the fan limit switch first. with burner burning on furnace,see if you can hear the limit switch click on. if not, shortly after chamber heats up, you will hear the high limit switch click and turn off the burner to the furnace.