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Trane XR90, LED flashes 2 times for error

151K views 56 replies 17 participants last post by  barker.patrick 
#1 ·
Trane XR90, LED flashes 2 times (flash-flash ---long pause--- flash-flash).

It is recycling itself, or failing to recycle...

So then the blower continues to blow air...but not warm air. No heat. Just a running fan, blowing air.

At times, I have "reset" it by powering the furnace off/on 2 times within 30 seconds as the manual advises. (Powering off at the breaker box.) This has cleared the problem many times for 30-40 days.

And then, it happens again. Same flash-flash. Blower blowing with no heat - just air.

Sometimes the "reset" technique mentioned above will not work at all (for a day or two). Then, all of a sudden, the "reset" works and heat is blowing again.

Any ideas?
 
#2 ·
From what you described, it sounds like it could be the high limit, but these things are hard to diagnose over the internet. Your best bet would be to see what the flashes mean by looking on the labels on the furnace door. The error codes are usually quick flashes followed by longer flashes, and also usually double digit to avoid confusion.
 
#3 ·
Trane XR90, LED flashes 2 times (flash-flash ---long pause--- flash-flash).


It is recycling itself, or failing to recycle...

So then the blower continues to blow air...but not warm air. No heat. Just a running fan, blowing air.

At times, I have "reset" it by powering the furnace off/on 2 times within 30 seconds as the manual advises. (Powering off at the breaker box.) This has cleared the problem many times for 30-40 days.

And then, it happens again. Same flash-flash. Blower blowing with no heat - just air.

Sometimes the "reset" technique mentioned above will not work at all (for a day or two). Then, all of a sudden, the "reset" works and heat is blowing again.

Any ideas?
James:


A 2 flash code means that the furnace is in a 'hard' lockout. This happens after 3 trials for ignition. You haven't listed the model and serial number of the furnace so it is hard to get real specific. XR90 is the family of 90+% furnace of Trance, but the model will be something like TUX... or TUY....ALSO, is it natural gas or LP?

1. To reset it in from a lock out you have to interrupt the power to the board for several seconds, which it sounds like you have done in the past. If it is a nuisance trip this will take care of it.

2. Some causes of lockout caused by failure to ignite can be an igniter that is getting weak (depending on the model number of the furnace whether it uses a silicon carbide or silicon nitrite igniter it should ohm out at 40-80 ohms cold (SC) and between 11-17 ohms for the (SN)); poor air/gas mixture (this can also happen during extremely cold weather when the gas company injects propane into the natural gas lines to keep the gas pressure up, or they haven't done it soon enough); the flame sensor may also be getting old or corroded up. These are some causes on intial start up. If it fails after it runs for some time there may be a crack in the heat exchanger that expands after it runs for some time and if it blows on the flame it can lift it off the flame sensor causing it to shut down.

3. And the reason the blower keeps running after the flame fails is to alert you that something is wrong with the furnace.

4. You mentioned that sometimes resetting doesn't work???? This could mean that the main board is bad OR you have a loose wire somewhere and when you are moving wires a connection is remade. Sometimes the connections become corroded or pitted so make sure that all the connections are clean and solid. After power down and up, does it try to light? What I mean does the igniter glow and the gas valve attempt to open? (Something else to consider - is the gas valve sticking?)
 
#4 ·
This sounds like a problem I am having with an older American Standard furnace. The board will tell you if you have a flame sensor, air pressure, or limit switch failure. The gas valve doesn't seem to want to stay open, it clicks on and off after a time, the control board is brand new and the voltage to the gas valve is constant when this happens. The flame is a nice blue not a bit of orange, so I don't think it is too rich. It will run anywhere from a minute to five minutes when this happens.
 
#5 ·
This sounds like a problem I am having with an older American Standard furnace. The board will tell you if you have a flame sensor, air pressure, or limit switch failure. The gas valve doesn't seem to want to stay open, it clicks on and off after a time, the control board is brand new and the voltage to the gas valve is constant when this happens. The flame is a nice blue not a bit of orange, so I don't think it is too rich. It will run anywhere from a minute to five minutes when this happens.
If you have constant 24 volts to the gas valve and it's turning off and on the the valve is bad.
 
#7 ·
Yes, if you have 24 volts to the gas valve and it shuts off the valve is bad. You say it runs for 1-5 minutes and then shuts off, so also be sure you are not losing flame contact with the flame sensor. It only takes a millisecond of loss contact with it to have the valve close. Loss of contact can be caused by the flame being blowen or lifted off byair leakage from a cracked heat exchanger or poor flame distribution if the burners are starting to get dirty. Just some things to check.
 
#8 ·
The gas valve is giving very audible clicks. The flame appears to be very steady with no drafts. The unit was cleaned last year. Being a dual fuel unit it doesn't run that much except in extreme weather and morning warm up. If the flame sensor was telling the control board there is no flame and the board was turning the valve off, then there would be a loss of voltage to the valve. Or would it be so fast I cannot see it on my digital voltmeter?

Also would the unit not give a flame sensor failure reading instead of recycle time out?
 
#11 ·
Those pressure switches can open and close faster then your meter can detect.
And the board won't report it as a pressure switch failure.
Generally comes back as a flame failure. Or a lock out from X retries.

Digital meters are not fast enough to catch it.

A manometer will though.
 
#12 ·
If it is definite audible click that is the solenoid valve in gas valve opening and closing and it sure sounds like loss of power to valve.

Like it has been said, it is tough to trouble shoot over the internet; we are just giving you possible scenarios...this is definitely one of those 'nuisance' problems that are a little tough to catch. From a service tech perspective it is always better to have a 'catastrophic' breakdown; much easier to diagnose and repair..Now it is a little like playing detective and eliminating all the possibilities one at a time until you find out which part is causing the issues. I hate being a parts changer and replacing everything until it works...I'm sure you don't want to be one either....plus it can get expensive.

One of those safeties (air switch, flame senser, gas valve, transformer (are you getting a good 24-27 volts from the secondary?); high limit; inducer motor, etc). Also be sure you have a good solid (earthen) ground to the furnace. Check between the white 'neutral' wire going to the furnace and the green 'ground' wire. You theoretically should have '0' volts, anything over 10-12 volts can cause you trouble with the board. At the same time make sure all your electrical connections are tight; a loose connection caused by vibration can sometimes cause it to act up.

You say you are only getting a 2 flash fault code; which means a hard lockout, so this only happens after a 3 trial for ignition failure.....if one of the other safeties is opening again theoretically you should be seeing a different fault code. I don't know what model number of furnace you have so I can't give you the different codes; depending on which one it is you can have up 7-9 diagnostic codes.....make sure it is not some other code than 2.
 
#13 · (Edited)
I know that this thread is a little old but I have been having the same problems with my trane xr90 furnace. it tries to cycle on three times, doesn't stay on, and then the fan blows cold air until someone notices. the error code is two blinking lights.

I pulled the front panels off and checked the ignitor (silicon nitrate), which seemed to be in order (13.5 ohms resistance). I watched as the furnace started and the flame came on every time from 8-20 seconds and then went out. I took out the flame sensor and scrubbed it a bit (it had just a little corrosion on it) and put it back in but it didn't seem to change anything. I also cleaned the intake/vent outside since I noticed that it had a few cobwebs in it, but it didn't help.

My gut feeling is that it's the flame sensor, but I really don't know that much about furnaces. Anyone have any thoughts?

Thanks.

Model# TUX080C942D3

Ps - I forgot to add that I can hear an audible click a second or two before the flame goes out. I am not sure if that is part of the normal cycle of shutting down the flame or if that is the valve switch losing power for another reason.
 
#15 ·
I checked the exhaust pipe on the outside of the house, but not inside the furnace. I did not want to disassemble the furnace too much without a service manual or some sort of know-how (i have nothing other than common sense to go by right now).

However, on closer inspection, I found out that the glow from the window actually wasn't from a flame being lit but actually from the ignitor itself. There is no flame, just the ignitor coming on and off. I can't believe I didn't notice that in the beginning.

Even though I tested the resistance of the ignitor and it seemed ok at 13.5 ohms resistance, I wondering if it could possibly be that. What else could it be?

Thanks for the reply.
 
#17 ·
On a whim, I decided to replace the ignitor. That did not seem to help. There is still no flame and the ignitor shuts off after 10 seconds or so.

I know at this point this should be a separate thread. Sorry.

Any thoughts?


I would make sure the ps is staying closed & check the other parts of the 24v circuit. If it fires up & goes back off could be ps or flame sensor , bad ground, board
 
#18 ·
i assume 'ps' means pressure switch? i really don't know that much about furnaces other than what I see when i take the front panels off and what I can gather off the internet. Is there a good parts list or service manual that I could possibly find?

I would test the ps to make sure it's closed (shouldn't it be open in the beginning?) but I'm not exactly sure which part this is. I would guess that it's the piece right off the main gas line coming in, but I can be sure. I'm also not sure how to test to make sure it's open or closed. any advice?
 
#20 ·
i checked the pressure switch while the furnace was off and it appeared open (infinite resistance on the multimeter). i did not bother firing up the furnace because i thought that the pressure switch should be closed (close to zero resistance) when the furnace is off. is this correct? and if so, does it look like my pressure switch needs replacing? can i verify this by temporarily putting a jumper wire from one terminal to the other on the pressure switch and firing the furnace up to see if the flame lights and stays on?

on a side note, there is no pressure hose from the exhaust fan. just one from the gas valve (i believe that is what it is), one from the combustion chamber, and the final leg to the pressure switch.

assuming the pressure switch is bad, i am wondering if the fact that the condensate hose was jammed down the drain was what was causing the issue. i will be putting in a condensate pump shortly anyway.

thanks for the help.
 
#22 · (Edited)
just after i posted last i found a few sites that said that the pressure switch should be open when the furnace is off. i turned the furnace on and the resistance jumped to zero and stayed there. i did pull the condensate tube out of the drain but that didn't seem to do much either.

i did finally check the voltage to the gas valve. i pulled the two wires off of the valve and read from the red wire to ground somewhere in the furnace. it read 0 volts when the inducer fan started, and stayed at zero when the ignitor came on. the ignitor glowed for 10 secs or so, like normal, and then there was the audible click from the lower area near the circuit board (i believe) and the ignitor turned off. around this time, i read about 26.5 volts from the red wire for a few seconds and then it went away.

any ideas?

ps - the original error code was two flashes of the diagnostic light (System lockout (retries or recycles exceeded))
 
#24 ·
it could be the pressure switch? the burners have never lit. the ignitor always glows and then shuts after 10 secs or so. no flame.

the switch could be bad even though there is no resistance between the terminals when the furnace is running? although i did find that while there was no resistance between the two terminals with the wires still attached, and there was 24v+ going from each lead/wire to ground, there was no voltage between the two leads/wires. i don't know if that means anything or not.

i did check the small pressure hoses and there didn't seem to be any obstruction. there was no obstruction that i can see on the intake pipe/grate, but I haven't checked the exhaust fan. it that necessary?

thanks for the help
 
#27 ·
the ignitor is certainly glowing and the furnace is not lighting. i did check the gas valve yesterday and i believe it might not getting power, though i am not entirely sure of how it's supposed to power up.

to check the voltage to the gas valve, this is what i did: i pulled the two wires off of the gas valve and started the furnace up. i then checked the voltage from the red wire to ground somewhere in the furnace and watched it for the first minute while the furnace started up. i read 0 volts when the inducer fan started, and it stayed at zero when the ignitor came on. the ignitor glowed for 10 secs or so, like normal, and then there was the audible click from the lower area near the circuit board (i believe) and the ignitor turned off. around this time, i read about 26.5 volts from the red wire for a few seconds and then it went away. i believe i also checked the black wire for voltage as well, but i didn't get anything.

is this a gas valve problem? a circuit board problem?

as a bit of background info, the furnace came with the house when i bought it a couple of years ago. i believe there was a flood at some point because the bottom of the furnace is pretty rusty (and the previous owner mentioned something about not hooking up the condensate drain properly or something like that). from what i can see, the water damage is only confined to the bottom of the furnace and it's metal walls and floor. the circuit board seems fine and the furnace ran fine for the past couple of winters. might there be a problem there?
 
#28 ·
Check for voltage between the 2 wires that are connected to the gas valve, while they are attached to the gas valve.

If you don't get 24 volts across the gas valve, but do when you read red to ground. Most likely. You have a limit or roll out switch open somewhere.
 
#32 ·
i took a quick picture of the upper portion of the furnace. i believe the switch at the bottom of the burner box is the high limit switch, and i checked that. the only think that i can think of that could possibly be the rollout switch would be the piece with two wires attached to it on the far wall below the burner box, but i don't see a reset button on it.

http://img543.imageshack.us/img543/1530/img4049j.jpg
 
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