my limit switch on my oil furnace does not shut off the burner when it hits the limit.I replaced the limit twice maybe I had a bad one still no luck . While furnace was running I took the thermostat off the wall and the burner keep running still . Can you tell me what to look for next. does the fossil fuel system have anything to do with this?

  • I don't know much about HVAC and so I might be Way off here.. but I believe the thermostat sends the signal to shut off the furnace? My guess is that it sends it once to lock it in and then sends another later when it's time to turn it off. The thermostat is where the temperature is checked? The switch within the unit is just a backup for overheating? Again, I don't know - just a guess - but could it be that the thermostat is bad?
    – TFK
    Feb 4, 2016 at 12:02
  • unpluged the thermostat off the wall and burner keeps running which should eliminate the thermostat
    – john
    Feb 4, 2016 at 14:10
  • 1
    What is the make and model of the furnace? Also, your post is a bit confusing. When you say "limit switch", do you mean the thermostat (the unit on the wall where you set the temperature), or the safety device within the furnace that shuts the unit down in case it overheats? What is the make and model of the thermostat?
    – Tester101
    Feb 4, 2016 at 14:25

1 Answer 1


The high limit being taken off the wall of the fire box it will never over heat. Try removing 1 of the leads to the switch if the furnace keeps running it is not the limit switch. Most of these limits have a manual reset button you need to press if they do overheat. If the furnace keeps going with the limit wire removed you need to have the controls fully checked out as this is a safety hazard.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.