I have a Goodman Janitrol GMPN080-4 model furnace that will not stay on.
The status light flashes 4 times which indicates an open Limit switch.
I had to replace the Limit Switch last year and figured it was the same thing, so I replaced it again yesterday.
When reset, the furnace comes on, the igniter heats up and ignites the gas. The furnace will then run for about 3 minutes and then will shut off and teh status light on the circuit board starts flashing 4 times again.
Any help or suggestions would be appreciated.
you may also clean the flame sensor on the opposite side as the ignitor.
remove it and scrape it with a knife, do not use sandpaper or emery paper on it, you will make matters worst.
should this along with clean filters and blower running not solve the problem, check for bad ground on the unit, make sure the transformer has one leg grounded as well as the board, then and only then would i replace the board.
remember, they do not take back tried electrical parts