Burner only comes on when I turn fan on

[MPV-13]

My heating system was working fine last night. When I got up this morning the temperature was at 68 degrees should have been 72 degrees. The honeywell digital termostat showed that it was in the heating cycle. But when I checked the furnace the burner wasn't firing. The pilot light was on however. I turned off the pilot, the furnace and trip the breaker. When I relit the pilot and turned on the heat the burner still wouldn't fire. But when I turned the fan switch to ON the burner fired up and the heat worked fine until I switch the fan back to auto. Any help would be appreciated! If there are any other details you need to figure out the problem let me know. Thank you for your help in advance.

[albright]

burner

its definetly a control problem, whether its your t-stat or your control board.

[lonestarheir]

Sounds like you have a high limit switch that is bad. one way to check for sure is to let just the fan run for about 5 min, turn it off, turn it back to heat and see if the burner fires for a short bit and then cuts out. If it does, you have found your problem. If not let us know.