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Old 11-01-2012, 07:39 PM   #1
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Trane XE80 burns out after 10 seconds


I've got a Trane XE80 gas furnace. I actually have two of these in the attic. Once works fine, the other does not. Worked great last season, first time this season and it doesn't work.

Symptoms: T-Stat on, IDM turns on, pressure valve pulls the diaphragm (I checked for blockage by gently sucking and blowing...no blockage), diaphragm does not pulse, igniter glows, gas turns on, gas ignites for about 10 seconds, then flame goes out. Retrys 3-4 times with same symptoms. Flashing red light (2 flashes) says Pressure valve open.

Troubleshooting thus far: took off hose for pressure valve and blew through it, and sucked on the diaphragm side gently (very gently). All good there. Took out the Flame sensor and cleaned it. Nothing. Traded the good flame sensor from my good furnace to the bad furnace. No change. BTW, the good furnace still works with the other flame sensor, so that is probably ruled out. Checked the voltage of the pressure switch before call for heat (0 VAC), with inductor fan on (0 VAC), while gas valve is opening (seems to fluctuate from 0-.6 VAC). BTW, I'm checking both wires on the switch, presuming one side is 'ground'. I checked my other good furnace as a control, and it read the same 0VAC.

I'm baffled! What am I missing?

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Old 11-01-2012, 09:57 PM   #2
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Trane XE80 burns out after 10 seconds


Clean the flame sensor

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Old 11-01-2012, 11:23 PM   #3
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Trane XE80 burns out after 10 seconds


1..check the heat exchanger for cracks.....2..try switching the pc board or flame safe control which ever it may have ,,,, 3,,,,switch out the presssure switch with other one on other furnace ,, but only change one thing at a time .process of ellimination .. let us know how u make out
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Old 11-02-2012, 12:06 AM   #4
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Trane XE80 burns out after 10 seconds


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1..check the heat exchanger for cracks.....2..try switching the pc board or flame safe control which ever it may have ,,,, 3,,,,switch out the presssure switch with other one on other furnace ,, but only change one thing at a time .process of ellimination .. let us know how u make out

NO! You don't know that the 2 furnaces are exactly the same. Just because they say XE80 does not mean that they are the same model.

What flash code are you getting from the control board?

Take the door off and with a call for heat from the thermostat post what the sequence of events are that happen?
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Old 11-02-2012, 12:09 AM   #5
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Trane XE80 burns out after 10 seconds


And tighten all ground wires. For flame rectification you need solid and clean ground connections.
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Old 11-02-2012, 06:38 PM   #6
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Trane XE80 burns out after 10 seconds


Thanks for the quick reply.

I've already cleaned and replaced the flame sensor.

I attempted to describe the sequence of events above. Am I missing the crux of the question?

I am getting 2 lights on the control panel.

I'll double check the grounding wires tonight. If that doesn't work, I may simply swap out the pressure switches.

I'll keep all posted.
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Old 11-02-2012, 06:41 PM   #7
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Trane XE80 burns out after 10 seconds


Its not the pressure switch. Just throwing parts at it is a waste of money and effort. Diagnose it properly. A 2 flash is ignition failure/lockout not pressure switch stuck open.
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Old 11-02-2012, 08:01 PM   #8
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Trane XE80 burns out after 10 seconds


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Checked the voltage of the pressure switch before call for heat (0 VAC), with inductor fan on (0 VAC), while gas valve is opening (seems to fluctuate from 0-.6 VAC). BTW, I'm checking both wires on the switch, presuming one side is 'ground'.
I'm baffled! What am I missing?
Check each to ground, not to each other. One side should always have 24 volts and the other should show it when the blower is running. Terminal to terminal will not show if the switch is working properly unless you are checking continuity.
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Old 11-03-2012, 10:56 AM   #9
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Trane XE80 burns out after 10 seconds


OK, based on great feedback (and proper 2 flash diagnostic), the control board says I have an ignition problem. I removed the ground for the control board, cleaned and re-seated it. I ohmed the wire between the flame sensor and the control board (0 ohms). tried a restart, and no difference in my symptoms. So I UNHOOKED the flame sensor and did a restart. No difference in symptoms. Again, the symptoms are that the Induction fan motor goes on, pulls the pressure switch, gas is flowing, ignitor kicks, flames ignite for about 2-3 seconds (sorry, not 10 seconds).

More research tells me that the control board ignores the flame sensor for the first couple of seconds (makes sense, that is why it burns for a few seconds) and then asks the flame sensor for the current and apparently it's not giving the appropriate current.

My next thought is to clean the burners to ensure this burner that the flame sensor is on is actually putting out the required flame. All three burners/flames 'look' the same, but who knows.

Additional feedback welcome. What else can cause an ignition failure/lockout?
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Old 11-03-2012, 11:16 AM   #10
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Trane XE80 burns out after 10 seconds


if burners, flame sensor, and ground are all clean and good.... Ideally you would check the flame signal, but it is doubt ful you have a meter capable of reading DC micro amps (uA). So, next item is the control board.
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Old 11-03-2012, 11:37 AM   #11
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Trane XE80 burns out after 10 seconds


Yes, you're right. Don't have a flame meter.

Burners clean, ground good, sensor good. I tend to agree with the control board.

So the possibility is that, although the board is saying 2 flashes, in reality it's bad and doesn't know what's going on, right? I guess a board cannot self diagnose itself...a crazy man doesn't think he's crazy.

Any steps to diagnose the board outside of remove and replace?
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Old 11-03-2012, 11:40 AM   #12
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Trane XE80 burns out after 10 seconds


Sorry, I meant I don't have a micro amp tester. But I'll go buy one if that would be the next logical step.
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Old 11-03-2012, 12:02 PM   #13
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Trane XE80 burns out after 10 seconds


Before you buy that meter (around $100) I would test the AC voltage on the flame sensor wire to ground while the burners are firing. If you already had a meter to test DC uA then I would have you test that first, but you don't so test the AC voltage instead. I would just buy a board rather than waste money on a meter when it is almost the cost of a board.
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Old 11-03-2012, 12:15 PM   #14
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Trane XE80 burns out after 10 seconds


Makes sense.

What's the voltage on the flame sensor supposed to be while the burners are on?
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Old 11-03-2012, 01:18 PM   #15
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Trane XE80 burns out after 10 seconds


go to sears and buy a decent multitester for around $50-$100 that tests microamps. looks like a u with a extra tail on the left. your burners may be corroded and dirty on their face. flame rectification is when the ac current from the sensor jumps thru the flame/gets rectified/changed to dc and MUST travel thru the burners back to the board thru the furnace chassis/ground wire. dirty burners or loose burners interrupt the circuit. clean the face of the one by the sensor with emery paper and get a tester and report back if that does not fix it.

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