Furnace burner and blower take turns

[Plumber69]

80% heil furnace. Burner runs for 2 minutes then shuts off, blower runs for 45 seconds then shuts off. This will just continue back and forth

 

[SShaw]

Sounds like the limit switch is cutting off the burner. The furnace could be overheating, or the limit switch could be set wrong, or gone bad.

 

[Sponsor]

 

[Plumber69]

Sounds like the limit switch is cutting off the burner. The furnace could be overheating, or the limit switch could be set wrong, or gone bad.

Jumped the limit switch, blower wouldn't come on. All I can think is its this thing

 

[SShaw]

I don't know what that thing is in the photo.

All I know is the limit switch has several functions which would be consistent with the behavior you saw. It will: 1) turn the fan ON after the burner starts and the HX gets hot enough, 2) keep the fan ON after the burner is off to remove excess heat from the HX, 3) turn the fan OFF after the HX cools down too much, and 4) cut off the burner OFF if the HX gets dangerously hot.

You should get an HVAC tech who knows oil to diagnose things. You don't want to take chances with oil.