Furnace Short Cycles Off and On
I have a Suburban SF30fq furnace that cycles the heater flame off and on about every three minutes while the coach is reaching the thermostat setting (technically called short cycling on the limit swi...
Forum Discussion
rogerck wrote:
I removed the inside furnace panel facing the trailer, then replaced the hi limit switch. After testing, the new switch also cycled with front panel removed. Maybe front panel with ducts attached is required for proper air flow across limit switch. Will try.
Removing the panel removes case pressure. That means the fresh air can move over the chamber freely without restrictions like a restricted duct. USUALLY, if the Hi limit is GOOD, the ductwork is inadequate(not enough for spec) or it is restricted. I would suspect insect nests INSIDE the combustion chamber restricting the flow inside the chamber creating hot spots. If I had the unit, I would be testing on the work bench to see if the problem stays when on the bench. I would take a rubber mallet and hit the chamber and then see if I hear nests inside the chamber. Doug
