high limit switch open

No, no, no. Today's lesson was on the NORSE codes, not the MORSE code.

And you misspelled '* ** *'.

If you have a clean air filter and the high limit still trips , then you have another/additional problem thats causing it to open. The switch itself may even be defective. Youll need to establish what the temperature rise is thru the furnace and compare that to the stated nameplate temperature rise plate/sticker on the furnace . More than likely , youre going to need a Professional come out to properly diagnose the furnace and get it working correctly. If you have a clean air filter, have ALL of your supply and return registers fully open , and the blower wheel isnt caked with dirt....they youve done all you can as a homeowner.

There is a *reason* why the high limit opened.... High limit switches are manual reset on purpose. Something caused it to trip, and the cause needs to be diagnosed and corrected.

You need to call your local competent HVAC tech to find out why the limit tripped, correct the problem, then re-set the limit.

I see people shutting half their supply registers thinking it's going to save them money but it makes the darned furnace overheat and shut down. The frail old mother of a late friend of mine had medical problems that caused her to be cold all the time. She closed the registers in her son's room after his death and she ran the heat when the outside temps were in the 50° to 60° range. Her Carrier packaged unit would not stay running unless it was very cold outside. Of course, because of her medical problems she liked an inside temperature of 80° to 85°F and the packaged unit was not going to keep operating with the restricted air flow.

TDD

Him This is a safety issue. The limit switch could be bad, or there maybe some other problem(s). The switch will reset when furnace is cooled off. Usually blower will run continuous until it is reset. If problem repeats, further investigation is needed. In my case(Carrier furnace) It was bad switch.

YES HE HAS TOO MANY dit's not enough da's