My question with my Trane XL 80 problem


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Old 11-28-15, 10:56 PM
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My question with my Trane XL 80 problem

I have a Trane XL 80 which is 15 years old. The problem I see is the system runs for a while (minutes to hours) and then shuts of with fan still running ! The error code is 2 blinks+ pause which means lockout. If I cycle the furnace power switch, the control boards gets reset and I see slow continuous blinking. When I turn on the thermostat, rapid continuous blinking asking for heat, the igniter plate gets hot and glows, the burners come on and it works for a while and then it locks out again. I had a technician come today and cleaned the flame sensor and it worked for 10 hours and locked out again.
What should I try next ?
I already paid the technician $225 for an emergency call, just to clean the flame sensor rod and watch everything working !!! I don't want to pay the technician few hundred dollars more to change the control board if that is not the problem.
Since this problem happens randomly, sometime in minutes and sometimes in hours, how would the technician know what the problem is ?
Thanks in advance.
 
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Old 11-28-15, 11:06 PM
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Welcome to the forums.

I moved you to your own thread. It's too confusing having multiple problems/different posters in the same thread.

What should I try next ?
You should call the technician back. It's pretty obvious to me he didn't fix the problem.
He cleaned the flame rod.... did he check it's operation with a meter ?
 
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Old 11-28-15, 11:17 PM
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The flame rectification should be measured. I would expect around 2.5 micro Amps DC.

The vacuum at the pressure switch should also be checked.
I would expect around 1 inch water column.
 
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Old 11-29-15, 07:51 AM
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Thank you for replies. Didn't know how to start my own thread.
My tenant took a video of the failure sequence:
https://goo.gl/photos/qPTMjf4D1Cw8ggNy6
Up to minute 8:30, all seems well with normal humming noise. At 8:30 when clicks are heard and system locks out (blink blink pause, ...), the fan is still running with much louder abnormal noise till he turns the power switch off. Could this be an obstruction in the blower ?
At least I can show you the failure now. Thanks for your help.
 
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Old 11-29-15, 08:19 AM
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I cannot view the video due to invalid perimeters?
 
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Old 11-29-15, 08:36 AM
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I can view the video but it only shows the front of the furnace and the blinking light. We can see the light blinking and we can hear the board operate but we can't see the burner.
 
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Old 11-29-15, 08:38 AM
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Could it be the Control board

I just called the technician and sent him the video of the failure sequence I posted. He insists of the issue being the control board. Being an engineer myself, doesn't the control board have a self test, with slow continuous flashing meaning all is good with the board itself ?
Thanks
 
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Old 11-29-15, 08:47 AM
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Reply to PJmax

Hi PJmax. Everything operates normally till lockout. Here is what happens:

1) thermostat is turned on
2) not sure when fan comes on, but seems normal
3) the igniter plate glows red and all 4 burners turn on
4) hot air coming out of the vents
5) hear clicking sound at minute 8:30, lockout, fan still blowing and noisy
6) turn power off after about about 2 minutes

Thanks
 
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Old 11-29-15, 08:58 AM
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It is very rarely a control board problem. The tech that came to your house should have checked the operation of the flame sensor with a meter. Shame on him if he didn't. We can't offer you much more help. Houston outlined what needs to be done.

If you allow him to put a control board in and it doesn't solve the problem... make sure you have.... in writing.... you can get your money back or you'll have bought an un-needed board and still have a problem.
 
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Old 11-29-15, 01:56 PM
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Thank you all

Thank you for all your feedbacks.
Have forwarded this thread to my technician.
God bless
 
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Old 11-29-15, 03:25 PM
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You typically get the lockout condition when the circuit board repeatedly fails to detect that the main burner is lit.

Obviously, you wouldn't want the main burner gas to be left on if the burners weren't lit, so if that condition is detected repeatedly, the burners are shut off and the diagnostic condition is displayed.

Causes of that condition can be several---

dirty flame sensor ---which has been cleaned

poor grounding of the circuit board, which MUST be well grounded to provide a complete circuit for the flame detection circuit.

poor operation of the flame detection circuit on the circuit board, which would require replacement of the circuit board.

Flame sensor not located so as to be engulfed by the burner flames, or fan operation that blows the burner flames away from the flame sensor.

What should have been done was to measure the DC current flowing through the flame sensor wire prior to cleaning it. If the flame sensor current was low and it rose to 5 uamps or so after cleaning it, that would suggest that the flame sensor was dirty.

IF the flame sensor current was normal, that would suggest a problem other than a dirty flame sensor.

It's still important to measure the flame sensor current to see what's happening there.

Also, measure the AC voltage being applied to the flame sensor. If that voltage goes to zero and the furnace locks out, you likely have a bad circuit board.

You likely have one of two problems ---- the circuit board ground may not be reliably being made, or a bad circuit board.

You may have to check the voltage and current until the furnace fails to identify the specific cause.

In my opinion, odds are that the circuit board is going bad and the problem will get worse until it wont operate at all.
 
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Old 11-29-15, 08:04 PM
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Hi SeattlePioneer and thanks for your input

I researched the web and found several useful videos/messages about my furnace problem. Cleaning the flame sensor is the most common and easy fix solution suggested, but I totally agree that This kind of intermittent problems must be solved by eliminating the cause step by step. Thanks for the details about the flame sensor behavior/current level/grounding and the fact that the whole flame sensor/control board loop must be tested.
I can see the flame sensor tip glowing red when the burners are on with no draft observed on the flames.
You are right on the point with the situation getting worst due to a bad control board. My tenants told me about the furnace blowing cold air about a week ago, but said later that the problem got fixed when they power cycled the furnace. The problem occurred within 10 minutes yesterday when my tenant could record and send me the video I shared.
I still HAVENT GOT AN ANSWER to a question I asked about controller board and would appreciate your help. Being a software engineer and having worked on firmware for control boards with various micro controllers / applications, typically what a "good" firmware does upon reset is it does a Powe On Self Test to make sure all the the board and all its interfaces are working ok. Doesn't the fact that the board LED start continuous slow flashing upon reset mean all is OK with the board itself ? I understand that the sensors and their connection to the board could be bad, but what about the board itself ?
You guys have helped me ask more intelligent questions of my technician and truly appreciated.
 
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Old 11-29-15, 08:32 PM
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Let me add this ... My thermostat

When they installed my XL 80 furnace 15 years ago, they also installed a new 1F80-24 white Rogers thermostat. I read in the spec that this is for a SINGLE stage furnace !
My tech told me that they have connected two of the connectors on the board with a wire to resolve this issue. I will try to paste the board pic here, hope it works. That is the brown wire at the lower left side of the board picture that connects W1 and W2. Any idea as what and why they have done that ? Should I have a dual stage thermostat to get full benefit of XL 80 dual speed now that I am at it ?
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Old 11-29-15, 11:05 PM
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Gas furnace control boards will attempt to light the burner three times.... if the burner doesn't light the board goes into lockout and shows the problem code by flashing the LED. When you turn the power off.... the lockout is released and the board starts over. These boards aren't that smart.
 
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Old 11-30-15, 04:32 PM
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Previous HVAC company backed out lol new company on its way :)

Thanks PJmax for clarification about the control board. After talking to the service manager and emails with previous service records, video clip of the failure and a link to this thread, the service manager told me this morning that they won't charge me for the $220 service call and I need to call another company !!! They should be truly ashamed and I hope they read this.
I have contacted the original HVAC company who installed my furnace and also replaced the control board 8 years ago. The owner told me that most probably it's the control board. I asked them to order the control board, so they can replace it when they come in 2 days I was told that the control board comes in a kit including the flames sensor and the igniter. This is even better as the usual suspects for this issue will be replaced.
Thanks guys for all you help. Will post here when all is done and hopefully the issue is fixed.
Happy holiday season
 
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Old 12-02-15, 03:09 PM
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New control board installed today

My new technician replaced the old control board with a new one (Trane Kit 15943). The new board is slimmer that the old one and and comes with the flame sensor and igniter which he installed both. Here is the link I found on web for this board: Trane KIT 15943 ignitor and control board kit
The technician told me that the control board/igniter/flame sensor come in a kit due to Voltage difference with the previous board. Anyone have experience with this board ? There is no red LED light showing on the door panel due to its slim size !
I will keep you posted if this new board resolve my intermittent lockout issue.
 
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Old 12-02-15, 03:49 PM
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the service manager told me this morning that they won't charge me for the $220 service call and I need to call another company !!! They should be truly ashamed and I hope they read this.
Actually I feel differently about that. It takes a big person to admit a mistake. They offered you a full refund which is pretty much unheard of. I give them one up for that.

Can't help you much on the kit. Hopefully your problems are resolved.
 
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Old 12-02-15, 06:56 PM
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Thanks PJmax, better error code mechanism in new board

You are right PJmax. I take that back. Although it took quite a few emails, phone calls and lots of my time, then that's life.

As the size of the new control board is slimmer than previous, now I don't see any light from the furnace panel tiny window. the error codes are different from before. There are 3 LEDs (green, Amber, red) on the board that indicate the normal/error codes.
 
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Old 12-06-15, 01:59 PM
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Replacing the control board fixed it

Changing the control board fixed the problem
I believe here were the reasons it could have been diagnosed as the control board issue:
1) The lockout occurred intermittently in minutes, hours or days, even though the error code was "no flame".
2) There was immediate lockout without any retires.
The new board has green/Amber/red LEDs and hence clearer error codes. I was also explained that they connect the w1 and w2 on control board to have the single speed thermostat work with this 2 speed furnace.
Thank you all for your inputs.
 
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Old 12-06-15, 03:13 PM
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Thanks for stopping back and letting us know the outcome. It's extremely important as others are also following and using your thread for themselves.... maybe not today but in the future. All our threads remain web searchable.
 
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Old 12-08-15, 08:34 AM
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Thanks PJmax

I have benefited a lot from this forum and so have many others. I googled "XL 80 problem" and found previous useful threads here.
PJmax, I have found forums like this where people collaborate and exchange ideas with help of experts like you as the "best use of Internet". I do try to contribute and finalize the threads, so it can be useful to others.
Thanks guys.
 
 

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