My heater will go through start up. Induction motor on, burner on, circulating fan on. It will run for a minute or two and then burner will cut out. LED light blinks 4 time, indicating limit or rollout switch is open. How can I trouble shoot what is wrong?

Thank you,

Tom

Look for the rollout switch and try a reset, most have a red reset button. Should be on the schematic. If it does it again, you may have a dirty filter, blocked flue, snow, bird nest etc. If it is a condensing heater, look for water or ice in the intake or exhaust pipe.

Thanks for the tips. The heater appeared to kick out on hi limit. After checking other things, I took the circulating fan out and clean and lubed it. That seemed to fix the problem. Apparently the fan was running slow enough to let the plenum overheat.