The heater won't stay on .

[datnguyen]

I have Lennox -80MGF-5 (EGC-2) burner unit.
The problem is the heater won't stay on as its should, I read the manual here what I -

1/. Board Diagnostic Paterns - DIAG 1 is Flashing and DIAG 2 in ON
2/. Mode Indication - Limit Switch Open
3/. Remedy - This LED pattern indicates that either the primary or secondary limit switch has open.Both switches are auto-reset.

It seems like it won't auto reset whenever its happen, Please give me your advise what I should do from here *

[nomadpeo]

you said it won't stay on. i'm assuming that means you have recycled it and it repeats the problem. when a limit switch opens, it is best to assume it is doing its job to protect from overheating. verify your filter and coil are not restricted and verify your fan is functioning properly. in some rare cases, a limit can go bad, but usually because it wore itself out doing its job. look for air flow issues.