Original message
| adentdude
 |  "GMP-125-4"
, posted Wed 20 Feb 18:50  
I have a Janitrol gas furnace which is about 12 years old (I know about time to replace it), it runs... sometimes. So the exhaust fan comes on and the igniter glows but no flame instead the igniter goes out after getting white hot and the system waits then trys again. Now, if I get lucky it will simply run, I mean the exhaust fan kicks on, about 8 seconds later the igniter glows , then the flame starts and we have heat. But usually the exhaust fan kicks on and off about 5 times and it doesn't start. Obviously the pressure switch works because the whole unit works. I checked to make sure the pressure switch tube is free of any debris. I removed the upper and lower panels and vacuumed the out the dust including on the circuit board. The filter is almost new and the exhaust fan is brand new. This has been an on going problem for 2 years now. My brother works in HVAC and every time he comes over to take a look I've had it off for over an hour and it kicks on with no problem. What is making the unit so moody? I read the posting from nupie 91 and I don't have that humming problem because I replaced that "vent" motor.
GMP 124 4
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Replies:
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| static
| "Re(1):GMP-125-4" , posted Wed 20 Feb 20:38
So you have verified that the pressure switch is actually closing? It probably is, but I have to ask.
Ummm...does this furnace have the tandem side by side blowers or only a single blower? And is it installed in the downflow position (burners at bottom, blower at top)?
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| | adentdude
| "Re(2):GMP-125-4" , posted Wed 20 Feb 20:43
how do I verify the pressure switch is closing? I used suction on the tube and it sounds like its opening and closing.
the single blower is under the burners.
GMP 124 4
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| | static
| "Re(3):GMP-125-4" , posted Wed 20 Feb 21:40:
You'd need to either unplug the wires from it and check for continuity across the two terminals with the vent motor running, well that would be the easiest way to do it.
The most common cause of this problem I find on those furnaces is if there is a automatic reset limit switch mounted on the blower housing, those seem to like to go bad. Check and see if your's has one of those, like behind the control board, will probably have two purple wires attatched to it, will be a black round knob looking thing about the size of a quarter, NO button in the middle like the ones on the burner box.
[this message was edited by static on Wed 20 Feb 21:41] |
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