Trane Electronic Ignition furnace won't light


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Old 03-12-07, 09:04 PM
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Trane Electronic Ignition furnace won't light

My Trane Electronic Ignition furnace lights intermittently.

The starting sequence seems to go correctly but the burners usually won't ignite until about 12 tries. The number of attempts is slowly increasing. Once it finally fires and runs a complete cycle, it most likely will fire the first time on the next cycle unless you let it cool down too long.

I have read that the gas valve should stay on for between 7 and 10 seconds before going off for lack of a flame. My gas burner only stays on for 3 seconds before turning off. I think that is too short a time.

One thing I'm not sure about is the length of time both the gas valve and the igniter are supposed to be on simultaneously in the ignition process. Precisely when my gas valve comes on, the igniter turns off and dims rapidly. This only allows a millisecond for the gas to ignite before the sequence is over. This does not make sense to me. However, my furnace has worked like this for years. Is the timing of these two events adjustable or is mine working correct.

If the igniter would stay on a second longer or the gas valve would stay on a second longer they would both be on at the same time and ignition would be more likely. As it is it takes multiple false starts until the burner will light. I think there is an unintended buildup of leftover gas from the previous gas valve on condition in the burner that finally helps light the burner when it finally does ignite.

- Replaced the electronic board myself last year (has worked fine since)
- Replaced igniter last week with new one (no change)
- Steel wooled the flame sensor yesterday (no change)

It's interesting that burner Ignition performance has slowly deteriorated over a period of a month. First it would ignite on the second try, then the next day the fourth or fith try etc. until now it takes about 12 tries.

When it finally ignites it will ignite the first time on the following cycles as long as it doesn't cool down for too long. What component can slowly degrade in performance. It would seem the igniter or the flame sensor. Both seem to be working fine.

Help, what to do now?
 
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Old 03-13-07, 09:13 AM
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What type of ignitor?
-Hot surface ignitor
-Spark?

How old is the furnace and model?
 
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Old 03-13-07, 02:13 PM
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You replaced the stuff already that I was about to talk about. Sounds like you already know a thing or two about these furnaces. I am not sure with YOUR furnace, where in the sequence the pressure switch comess in...if that would allow for ignition ATTEMPT first. (But I would not think so) Easy to test for though to see if pressure switch remains closed as the inducer runs.

Sadly, it is conceivable that your 1 year old ignition control board went out on you already. But you have to carefully make sure that ALL your safety switches are closed and that...

[Important]... the ignitor is glowing real good. You may want to take an ohms test on this also as sadly, yet cheaper than the control board!, THESE can fail in 1 year, and I have had them DO so...and they can glow and everything and still be failed! (I had one 2 years ago, about, that lasted exactly 1 year to the day, as I had it recorded on the furnace! They gave me a new one, free...and that was indeed the problem) They have to glow super bright to ignite the gas. If there is beyond a certain amount of resistance in the HSI ignitor, they can glow...but just not glow QUITE bright enough to ignite the gas, and imediately the gas valve shuts off.
 
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Old 03-13-07, 08:36 PM
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Originally Posted by Jay11J View Post
What type of ignitor?
-Hot surface ignitor
-Spark?

How old is the furnace and model?
The igniter is HSI type. The furnace is 10 year old Trane Electronic Ignition model# TDE060A936K2
 
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Old 03-14-07, 06:36 AM
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Do you have an OHM meter to ohm out the HSI? Like Dave said, it may look lilke it's OK. but it's not really doing it's job.

Also, make sure you got good grounding at all ground contacts to ground wire from the furnace back to the breaker box.
 
 

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