Trane XE78 - No Gas

Old 10-21-03, 10:08 AM
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Trane XE78 - No Gas

Hey All,
First time poster so please bear with me. I am an electronics technician so I should be able to follow most all of the conversation. I will go right down the list of 7 things you want to see so I dont miss anything:

1) Northern Alabama - current highs of 75, lows of 50
2) All brick, 2100sq ft, 1 level, furnace in attic, condenser outside
3) Trane, XE78, 11 years old, single stage
4) Natural Gas
5&6) N/A
7) Digital Thermostat
8) Over the past 2 years, I have replaced the glow type igniter and burnished the flame sensor. Thats it..(filter was clean)

Current intermittent problem - When the call for heat is requested, I hear a relay click and the igniter glows, but no Gas ignites.. After 8 seconds or so the igniter goes out. The igniter then comes back on and goes out 8 seconds later after no gas ignites. This is repeated 3 times and then the blower comes on blowing cold air through the house. This morning, after 10 minutes, I actually had to lower the thermostat, kick on the A/C, then turn it off to get the blower to stop.

I get the following flashes from the control module:

2 flashes/second continuous - this happened when the Call for Heat was initilized and continued until the blower came on.

2 flashes, then nothing, then 2 flashes, then nothing, repeating - this happened when the blower was on but there was no flame

1 flash/second continuous - Unit was off

A guy came and checked it on Friday, but, of course, the unit would not fail while he was there. It worked through the weekend and then failed last night. I called the heating company back out, but they cant come until tomorrow. I was just wondering if there was anything I could check in the meantime...

thx for the help
Old 10-21-03, 10:29 AM
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I would check gas pressure at the outlet of the gas valve on the furnace.
Old 10-21-03, 02:41 PM
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I was hoping for an electronics solution as that is what I specialize in....I guess I will have to have a service guy look at it....



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