tstex
Silver Supporter
If it was the high limit, the error code would be LO (Limit Open).
If the system does not acknowledge that the limit opened, it won't shut off the gas.
The limit isn't in series with the gas valve where it can cut power to the valve.
The limit is monitored by the board and if the board sees the limit open, then it cuts power to the valve and gives a LO code.
IF means that flame rectification was lost.
Burner inspection and cleaning:
With the heater on, remove the front door and make a visual inspection of the main burners through the inspection window. The main burner flames should be about 1⁄2 to 2 inches in height and should not “lift” off the ports of the burners. See Figure 47.
A normal flame is blue, without yellow tips. Yellow tips or a totally yellow or “lazy” flame may be an indication of a fuel-rich mixture due to restricted air openings, including spider nests in the burner and/or orifices.
All burners should be brushed with a wire brush and be free of lint, dust and spider webs before each season of use. Burners with damaged ports must be replaced.