Furnace Ignition Problem


Old 12-13-02, 02:39 PM
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Angry Lennox G26 gas furnace - no ignitor spark

I have 4 lennox G26 series gas furnaces in my house. One is currently broken - no spark at the ignitor.

Fortunately I have the ablity to monitor one of the other furnaces that is working to review the "firing sequence". Normally, the vent blower starts up, after about 5 seconds the pressure sensor picks up that the blower is working and a green LED comes on on the Intermitant Ignitor Control Box, I then hear and feel a click in the gas valve, then immediately after the click there is another click that I believe comes from the Intermitant Ignitor Control and then the ignitor starts sparking, the pilot gets lit, then the burner comes on.

On the broken unit, I get the click at the gas valve, but no second click and no sparking ignitor. I then turn power off to the unit, wiggle the wire conections a bit or tap on the Intermittant ignitor Control box, turn power back on and she starts up.

So far logic tells me I need the Ignitor Control box, but wasn't sure if the gas valave had anything to do with the failure since it is an electro-mechanical part of the whole start up. Any thoughts?????? Thanks!
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Old 12-13-02, 03:23 PM
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By turning off the electric you are resetting the control module. I am assuming that the unit will run until the t'stat is satisfied and will not start again. Go for the new control module.
Old 12-13-02, 04:21 PM
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Lightbulb follow up

Thanks for the quick reply. Interestingly, just turning off and on the power alone does not cause the unit to start up. I must shake or tap the control box. This in itself is telling me I should have pinpointed the problem. I am just hoping I don't go out and spend some big dollars on a control module and then thats not it!
Old 12-13-02, 08:18 PM
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Can you open that control module? You may simply have a loose connection inside.
Old 12-14-02, 07:21 AM
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Exclamation A new stage of troubleshooting!

Well, before I tear into the control unit or buy another one (about $150) I have reviewed what actions I take to make the furnace work again. It now seems that when I turn off, then turn on the gas valve, it starts up. It is a Honeywell gas valve with three slide on wire connectors on the top. Based on the feel, the on off really seems like an electric switch more than turning any kind of valve, and there is a definite interconnect between the gas valve and the ignitor control. Normally I hear and feel a click in the gas valve right before the ignitor starts to spark.

Sooooooo ... now I am concentrating on the gas valve. I am trying to make absolutely sure of what the issue is before just swapping parts! Also, I wonder if dirt getting into the valve may have caused this. I am on propane where I live and I almost ran out last week. I believe the furnace was running when they filled my tank and I am thinking that some dirt from the bottom of the tank got stirred up and went in the valve. Any thoughts???
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