Whirlpool Furnace Short-cycles


Old 11-22-04, 12:11 PM
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Whirlpool Furnace Short-cycles


I have a 17 year old Whirlpool gas furnace that is trying to start, but can not. The thermostat calls for heat, the igniter sparks, the gas comes on and ignites for a second or two, then goes out. It continuously cycles like this several times a minute. From time to time the blower will come on for a minute then turn off. I was able to get it started this morning by turning off power to the furnace for several minutes then turning it back on. It started and ran fine for one full cycle after that.

Thanks for your help.
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Old 11-22-04, 04:56 PM
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hard to say. i would first clean the flame sensor and see what happens. it is a rod, more than likely, at the burner furthest from the spark ignitor location
Old 11-26-04, 04:39 AM
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My unit has a combination igniter / sensor. It didn't look bad though I did clean and and the connections with steel wool. The furnace is still experiencing the same problem. It will get to the point that the burners lite and then it self extinguishes after a couple seconds or less.
Old 11-26-04, 09:41 AM
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It does sound as if flame sensor doesn't "sense" the heat - that's why it goes off. I'd try using volt-ohm meter to see if it generates anything (using stove gas to heat it up) or something...
Old 11-28-04, 07:30 AM
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Short-cycle Whirlpool

My furnace is doing the same thing. If you turn up the thermostat, you'll hear the exhaust fan start. Then a click and soft "whoompf" of the flames starting. Within five seconds the flame stops and the cycle starts over. This "Click,Whoompf" cycle is waking us up at night. I'll look at the flame sensor thingy, clean and test it with an ohmeter and get back to you with my findings.


Old 11-28-04, 08:36 AM
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Short-cycle whirlpool

Well, there is no flame sensor near the burners. Just an igniter that's connected to a module with a spark plug wire. There is a fan limit switch that turns as it heats up. It is connected to a relay that controls the main blower. Hmmmmm.

Old 11-28-04, 03:00 PM
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Short-cycle update

Well, now I understand that the igniter is also the flame sensor. Somehow, when the flame from the pilot is running over the tip, the ignition module senses a current to ground. The advice from an HVAC guy was to make sure the tip is clean and make sure the ground wire has a good connection to the pilot/igniter. Having done that, the problem is still happening. I jumpered out the thermostat to prove that out and it still short cycled. I found the instructions for the ignition module on the web:


The troubleshooting flowchart included in the .pdf file basically says "replace the module".

I'll let you know if that was the problem.


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