1989 Trane XL80 intermittent lighting/quiting mid cycle?????

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Old 12-18-12, 02:43 PM
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1989 Trane XL80 intermittent lighting/quiting mid cycle?????

I have a Trane XL80 model TDD060A936A0 furnace. I have been having problems with it lighting for a while now. I think I may know what is wrong but want a second opinion.

When I turn the thermostat up to call for heat it starts up the internal exhaust fan. the pressure switch clicks and the ignitor glows. After about 30 seconds the Ignitor panel clicks and the gas starts.....sometimes. Many times it clicks and nothing happens with gas so the ignitor cycles off. then the pressure switch calls again and it turns back on glowing through another cycle. If that fails I believe it kicks into a lockout mode and the exhaust fan just runs and runs until I turn it off at the thermostat and start the sequence over again. Now to troubleshoot, I have cleared and checked the tube to the pressure switch and the electrical to it. All seems fine there. Next I took the flue off and cleaned it all out so there wasn't any issue of backpressure or anything that could be the cause. I took the flame sensor out and cleaned it with a wire brush and reinstalled. I also took the cover off the furnace thermostat and when it does get flame I watch it cycle correctly and the fans seem to kick on at the right temp settings.

Now, when it fails, I have tried the suggestion of a service tech of tapping on the Grey ignitor panel. Most of the time if I do that after the 30 seconds of heat up I can get it to click and produce flame. Sometimes it will stay on, other times it starts and then shuts right back off. If I then tap some more it will restart most of the time. Eventually though after a few minutes or sometimes it may run for a day but eventually it will shut off again and I have to tap it to get it going again. This leads me to believe I need to replace that ignitor board. It is a FENWAL part No 05-246266-203. The service tech said if I replaced it I would need the Kit 9163 which is almost $600 (his price). In searches online I can get that kit for closer to $300. I also saw there is a replacement option for that FENWAL part with PN 35-655801-013 which is only $138.

Is it truly an option to replace the old Ignitor board with a newer model or do I need to step up to the kit with the higher price?

Any info/help would be greatly appreciated.
Thanks!
Dave
 
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Old 12-18-12, 03:39 PM
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If the pressure switch is opening, you have a 100% probability that the furnace will shut off. Solve that problem first!


Does the furnace vent into a masonry chimney or a metal vent? If you haven't already, take the vent pipe out of the chimney and vacuum any debris that has accumulated at the bottom of the chimney. Inspect the chimney for any obstructions.

Will the pressure switch close and the furnace light reliably if the vent pipe is disconnected?



There are NUMEROUS issues that will cause the pressure switch to open. You need to work through those one by one until the cause of the problem is determined.
 
  #3  
Old 12-19-12, 01:20 PM
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Thanks for the reply. It vents into a metal vent. I have taken the pipe off from the furnace up and over to the vertical stack and cleaned it all out completely. I haven't gone up on the roof to check the top cap but that is about the only thing that is left unchecked on the chimney.

As for the pressure switch. I will check tonight by taking the vent pipe off and see if it will light consistently or not. I guess I just assumed that with tapping on the ignitor board and the furnace lighting it ruled out the switch but now you have me thinking. So when the switch activates and turns on the glow ignitor, is it supposed to then open or shut off after the flame starts? If so can I check that with a meter or something?
Thanks again!
 
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