Trane XV90 extinguishing flame at start up.....??????

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Old 11-14-10, 03:28 AM
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Trane XV90 extinguishing flame at start up.....??????

My Trane XV90 is having some ongoing issues, the furnace went out last week and now will not ignite. The sequence of events are as follows: Turn the unit on- inducer fan turns on and comes up to speed-igniter glows-gas valve opens- furnace ignites jets- jets are immediately extinguishes. I cannot hear the pressure switches clicking and I do believe they are good. The one time when it lit and stayed on was when I cleaned the flame sensor with a scotch bite pad. Everything looks fine, it just does not work. Anyone have any ideas? Thanks, Earl.
 
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Old 11-14-10, 08:56 AM
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What fault code are you getting on the board?

Make sure you intake is not blocked.
 
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Old 11-14-10, 10:27 AM
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You never said when you last Scotchbrite pad cleaned. Although - if the flame IMMEDIATELY goes out (say in 1/2 scecond), that would not be the issue. Only would be the issue if flame went out after flame was on for 3-4 seconds.

I would not rely on going by a click sound to determine status of pressure switch. Test the switch with voltmeter during operation of furnace sequence.
 
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Old 11-14-10, 03:31 PM
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The fault code is "External Lockout (Retries or Recycles Exceeded)". I take it this is when it has tried unsuccesfully to light three times. The intake in not blocked and it ran last week for several days without issue. When it did run the wife kept it hillbilly hot until I turned it down so it's possible it never had to re-lite. The flame ignites on the first jet and goes across to the last jet and within a second the gas valve extinguishes the flame and the process starts over after the inducer fan runs thru the purge cycle. The builder posisioned the unit against the wall and I have about 9 inches for me to stick my way to plump pumpkin head in there to see much more, I have been using mirrors to get this far. I am tempted to try to move the flame sensor to the third jet to see if that helps. Earl.

I will try to reclean the
 
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Old 11-14-10, 08:01 PM
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Are yo able to lift out the intake vent on the furnace? If you can, try running it.

If you can't, then try firing it with the burner cover off.
 
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Old 11-14-10, 10:32 PM
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While trying to check the pressure switches and letting the furnace go thru its routine, it started working again. Ran for a couple hours then back to extinguishing the flame. Pressure switches check out as working. I took it apart to a degree and was able to scotch brite the flame sensor again as well as drop the gas jets and run a sewing needle in them to make sure they are not obstructed. The “tubes” where the gas goes thru is open and looks to be fine. I also wiggled the flame sensor to be in line with the gas jet. Removing the burner cover didn’t help. I also removed both vents to make sure they were not causing any issues, no help. This is set up for propane and I have good pressure. Is it possible that my gas valve is not opening enough and I’m not getting the flame I need to the flame sensor in time? Any ideas? Earl
 
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Old 11-14-10, 10:46 PM
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The flame sensor is only half of the circuit. Your flame conducts power to the burners for flame rectification. Clean the burner ends near the flame sensor and check for a good ground.

What trouble code is displayed after you reset power and it fails to light the first time?
Pressure switch or flame sensor error?
 
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Old 11-14-10, 10:47 PM
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The ends are clean and have no buildup. The flame sensor is mounted very,very tight On the picture below, is the little screw on top of the gas valve an adjustment screw or something I should not touch?


 

Last edited by bigearl67; 11-14-10 at 10:51 PM. Reason: additional
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Old 11-14-10, 10:51 PM
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I would not recommend adjusting the gas valve without a manometer.

If pressure switch error is displayed when you reset power and it fails to run the first time, check the furnace condensate drain.
 
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Old 11-14-10, 11:15 PM
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I checked the drain and it’s clear. I am not getting a pressure switch error; it just extinguishes the flame at ignition. I also checked the wire to the flame sensor and it’s tight and seems to be fine. I get a “flame sensed when no flame should be present” indicator light when I try to ignite the furnace with the wire off the sensor.
 
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Old 11-14-10, 11:34 PM
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You need an AC voltmeter to do some basic checks and determine what is shutting off the burners.

That could be the thermostat, pressure switch, unreliable ignition control or an unreliable gas supply. A poor electrical connection could cause erratic operation of the furnace.

In short, you need to be systematic about checking one thing after another until you determine which system is shutting off the furnace.
 
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Old 11-15-10, 06:11 AM
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At it again, the pressure switches check out as does the ground on the unit (chassis). The unit is not getting a fault per se, but a “cycled out” light. It is calling for heat from the thermostat. I believe I can rule these out. I tried rapping the gas valve on my outside tank and triple checked to make sure the valve was all the way open. I have a “drain” at the cut off going into my unit and when I took of the end cap I got what appeared to me to be decent pressure and surprisingly, a little oil. I did get it operating by swinging the flame sensor to position it in front of the third gas jet instead of the final, fourth jet. It came on with the second attempt. So I believe it is the gas valve? There is a “Hi” wire going into it so am I thinking correctly that it has two stages of opening? Is it possible that it lights on the Hi cannel and that is not working? I did also remove all the quick connect fittings and cleaned them, to no improvement. The gas valve (36E54- 201) cost 300 bucks to replace while darn near every other Trane valve I can find similar cost 50 to 70 bucks. I need to evict Murphy from this unit. Earl.
 
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Old 11-15-10, 06:19 AM
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I did not get an answer on my question...

Anytime when it tries to fire off, was the burner cover off, or on in place?

don't be replacing parts until you are able to take a meter and take some readings to know for sure what is the cause.

On the t-stat, are you calling for 1st or 2nd stage of heat?
 
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Old 11-15-10, 06:48 PM
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The unit fails to light with the cover on or off. It has been operating all day with the flame sensor turned to the third jet. No pilot. The indicator light just blinks rapid when calling for heat and I am not sure what stage it is calling for. I replaced the t-stat early on since it was first suspect. Earl.
 
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Old 11-15-10, 08:27 PM
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Make sure W1 color matches W1 at the furnace and same for W2 to W2.
 
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Old 11-16-10, 03:50 PM
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Originally Posted by bigearl67 View Post
The unit fails to light with the cover on or off. It has been operating all day with the flame sensor turned to the third jet. No pilot. The indicator light just blinks rapid when calling for heat and I am not sure what stage it is calling for. I replaced the t-stat early on since it was first suspect. Earl.

??? You said it has been operating all day after you did what you did. Are you still wondering what your main problem is, even though you made it work by repositioning the flame sensor?
 
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Old 11-19-10, 03:54 AM
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Yes, I am still not positive. Is the gas valve not opening as far as it should and if so is it because it’s opening only to a predescribed value due to it being a two stage unit or if it just wore out and is not functioning properly? Is the t-stat calling for an incorrect value (wired properly) or is it just not working. Possible I am not getting enough propane pressure at the tank/line or even the sensor could be faulty (doubtful). I am hearing a “whistling” when the gas first ignites. I am clueless about this. I have been out of town for a couple of days and it’s still working ok. Should I just leave well enough alone? Earl.
 
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Old 11-19-10, 03:41 PM
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When you fooled the furnace by setting flame sensor at first burner - when the burners all operate, can you see good enough(even if you have to remove a cover) to see if the last burner that should have the flame sensor at it is burning equally as strong as the first 2?
 
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Old 11-19-10, 03:46 PM
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When you fooled the furnace by setting flame sensor at first burner -when the burners all operate, can you see good enough(even if you hgave to remove a cover) to see if the burner that should have the flame sensor at it is burning equally as strong as the first 2?

Because you were able to make the furnace work, doing what you did with the flame sensor, that means the problem can only be with the flame sensor; either it's cleanliness or it's positioning - or the gas pressure, or how the gas is able to move through the burners or cross over. It has to be one of these issues.
 
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Old 11-20-10, 09:21 AM
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Thanks Ecman51, I just moved it to the third jet instead of the fourth and yes, I am getting strong flame at that fourth jet, but I do suspect it’s not as strong as it ought to be and that could explain the “whistling” I am hearing. My understanding is the flame sensor is just a metal switch that trips when heat is applied. I cleaned it off several times so far and it seems to be working. At this point I will just leave well enough alone and put replacing the sensor on my to-do list. Thanks, Earl.
 
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Old 11-20-10, 11:03 AM
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Well, I wouldn't continue to defeat the safety the flame sensor provides. If that buner is say not working properly, CO levels could go up.
 
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