Trane XV95 not firing randomly and 2 red flashes


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Old 02-17-14, 05:42 PM
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Question Trane XV95 not firing randomly and 2 red flashes

Furnace is about 6 years old and I have inherited with the house we bought.

This problem is hunting me for good part of the winter. We have been using wood burning stove all the time and we would never notice the furnace not working until some really cold weather came in and we forgot to add firewood mid-night.

There was 2 red flash error code back then, but I was able to figure out that the problem was HSI not going on. So, replaced HSI and viola, furnace worked. But after day or so, I noticed it doesn't fire every time. Inducer goes on, HSI goes on, then there are 3 scenarios:
A - no fire at all
B - it fires for 3 seconds, goes off
C - it fires normally

After A and B happened couple times (4?), furnace fan would go on for about 1 hour or so.

So, I cleaned the flame sensor and then replaced it altogether. Cleaned it again just couple days ago (after 3 months of use)

I also cleaned all tubing going to pressure switch with compressed air (unhooked of course) and blew through nipple going to fire box.

Supply and exhaust piping is new and clean of any restrictions. Fairly short too (about 10ft total each), with just 3 elbows each. 3" solid PVC.

What else can I do to troubleshoot it? Use paper clip to make sure nipples on pressure switch (it's a dual unit) are clean?

I did read several stories about XV95 heat exchangers cracking wide open and I do have CO and smoke alarms on all levels of my home. No alarms yet.

One thing I would like to do is to reset the code on the board. 2 flashes don't tell me anything. Manual says to power up with G energized (so is it enough to just turn the furnace on with fan ON) and then connect R with W1 3 times within 6 seconds. Is that correct?
 
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Old 02-18-14, 12:50 PM
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Just to follow up, one could blame it on faulty flame sensor, but what about situation when there is no flame altogether (A). HSI goes on, hear relay click, HSI goes off. Flame sensor is just 3 months old and just has been cleaned too.

I would have to watch how often A, B and C happens but don't think it matters. It's totally random.
 
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Old 02-24-14, 11:45 AM
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I reset the flash counter and it was code-free for some time. Few days later now, I noticed the fan running cold in speed, looked at the furnace and it's flashing 2 red again.

I cleaned the tips on both pressure switches, blew air through all tubing. New flame sensor, new HSI.

Am I down to bad pressure switch(es) and/or gas valve?
 
 

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