Trane XE80 problem


  #1  
Old 12-12-10, 01:28 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Trane XE80 problem

I have a Trane XE80 that is about 15 years old. Recently (just since the cold hit this year) it has developed a problem:

When heat is called for, the furnace starts in the normal way:
1. purge fan runs
2. ignitor warms up
3. gas flows
4. burners ignite

After 15-30 seconds, the burners flame out 2-5 times in rapid succession (the rate is about 5 clicks per second), accompanied by a click each time. Sometimes they stay lit, sometimes they go out completely, and return to step 1.

Sometimes the burners stay running for the whole heat cycle (until the thermostat says heat goal is reached), and sometimes it does the flame-out cycle the whole time.

The LED is flashing "normal" the whole time. The burner flames are strong and steady--there doesn't seem to be any restriction in the gas flow. I removed and cleaned the flame sensor with steel wool--this appeared to fix the problem, but the problem returned later that day.

Any ideas?
 
  #2  
Old 12-12-10, 01:55 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
Check to see if the pressure switch is opening or if it has a nice 24 VAC voltage while this syptom is occurring.

If the voltage is steady, I'd measure the DC micro amps flowing along the wire to the flame sensor when the burners are lit. I take it the flame sensor has the tip engulfed in the burner flames while that is happening?
 
  #3  
Old 12-12-10, 01:57 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the input--how do I do that?

I am no HVAC technician, but I do have a multimeter and basic mechanical skills. How do I check if the pressure switch is opening?
 
  #4  
Old 12-12-10, 04:57 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
S/P must be watching football or otherwise occupied so I'll see what I can do to help.

To check the pressure switch clip one lead of your meter to each wire terminal on the switch. Hopefully there's enough room to get your meter clips on with the wires connected.
Fire up the furnace & watch the volt reading. Fluctuation in voltage indicates the switch is opening, if only momentarily. A closed switch will read 0 volts across it.
 
  #5  
Old 12-12-10, 05:22 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sorry for the dumb questions, but what/where is the pressure switch? The only switch I know is the switch that tells the furnace that the cover is on.
 
  #6  
Old 12-12-10, 05:31 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
The only dumb question is the one not asked. If we came to you for help you wouldn't expect us to know everything about your field of expertise.

On the purge fan there should be a small hose. Follow that hose & it should take you to the pressure switch (normally round & about 2" across).
 
  #7  
Old 12-13-10, 10:17 AM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Okay....BAD MORNING WAKEUP!! I woke up to a 58 degree house. I checked for the hose on the purge fan, and found no hose anywhere on the entire furnace. What kind of hose should it be? Clear, or a small black one like a vacuum line on a car engine, or...? The LED was flashing twice.

I took the cover off and looked around, then held the door-closed switch to see if it would start. LED flashing fast (calling for heat), purge fan ran, then NO ignitor, then gas flowed. No ignition, so it shut off. This will be an expensive and poorly timed (cash is short) service call, so if you guys could help, it would be a real life- and wallet-saver.
 
  #8  
Old 12-13-10, 10:34 AM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
If the hot surface ignitior didn't turn on and get white hot, and the main burner gas switched on, it's likely that the hot surface ignitor is burned out.

You can remove and inspect the HSI for a crack, often outlined by a white powder. If it's burned out, replace it.

I recommend getting two so you have a spare for the next time.
 
  #9  
Old 12-13-10, 10:37 AM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
I will check that--thank you!

Is it burned out ONLY if there is a visible crack? What is the voltage to the ignitor? Can I test that with the meter?
 
  #10  
Old 12-13-10, 10:44 AM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
95% of the time the ignitor is bad with the symptoms you describe, so check that first.
 
  #11  
Old 12-13-10, 10:46 AM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
OK--just removed the ignitor, and there is indeed a crack outlined by powder. Good job, guys! I am off to the HVAC store to get a replacement.
 
  #12  
Old 12-13-10, 11:24 AM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
New ignitor, so far so good!
 
  #13  
Old 12-13-10, 01:04 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
It ran smoothly for a little while, then started replaying the original problem. It is actually flaming out more times now--at one point it ran for 60 seconds, then clicked 9 times before going out completely. The click is coming from the gas valve above the burners (actuator?). I took a video of it with my phone the last time, and uploaded it to YouTube, so if this explanation of the problem does not cover it, you can watch the video and see if it makes more sense. It starts to flame out at about 00:19
YouTube - Video_121310_001.3gp
http://www.youtube.com/watch?v=Qj49CdJV84I
 
  #14  
Old 12-13-10, 03:16 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Can you post some pictures of the furnace with good lighting? We need good clear pictures wide angle & close ups if you can, it could be a big help. You can post them on Photobucket.com or similar photo hosting site & provide a link here.
 
  #15  
Old 12-13-10, 05:48 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
My opinion is that you haven't investigated the fundamentals of what is causing the furnace to shut off. If you want to do that, go back to post #2 on this thread and start there.


Something is turning the furnace off. That could be a bad power supply, thermostat, pressure switch opening, bad circuit board or a variety of other things.

The only way to know the cause of the problem is to investigate each possible problem and see if that is causing the burners to shut off.
 
  #16  
Old 12-14-10, 01:00 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
I understand what you're saying, but I don't know where the pressure switch is. I read what you said about following the hose from the purge fan, but I found NO hoses in the entire furnace. I will post some pictures shortly.
 
  #17  
Old 12-14-10, 01:15 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
  #18  
Old 12-14-10, 03:30 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
On picture #8 the pressure switch is the circular part on the right with the orange wire going to it.

There ought to be a rubber hose about .25" in diameter from the pressure switch going to the right where the inducer motor is. But I don't see it ---nor do I see a fitting on the inducer motor housing for tubing to be fitted to.


I don't suppose there a rubber house on the back of the pressure switch where it can't be seen?

It doesn't make sense to have a pressure switch and no tubing connected for it to measure.
 
  #19  
Old 12-14-10, 03:53 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
SeattlePioneer & Grady--Thanks for the clarification on the pressure switch. I didn't see the hose--it went from the back of the pressure switch straight back to the chamber, and it was obstructed by the switch's mounting bracket.

I hooked up the multimeter to the connectors on the pressure switch. When I turned on the breaker, it jumped to 27.2 VAC for a second or two (system check?), then back to 0.

The purge fan ran, the ignitor glowed, the burners lit, and the blower started. When it flamed out, the pressure switch briefly showed 23.4 VAC. After it restarted, the next flameout showed 27 VAC, and it held there for 3-4 seconds before everything recycled again. EDIT--I should mention that the voltage jump coincides with the flameout, it does not seem to precede it.

Does this tell you anything?
 
  #20  
Old 12-14-10, 03:57 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
Heh, heh! You KNOW you are good when you know things are there that the person looking at them doesn't see!

That's not to be critical --- I've never seen tubing hidden like that and it's obviously a poor design practice.
 
  #21  
Old 12-14-10, 04:00 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Good job, SP!

My areas of attempted expertise are in widely varying fields. HVAC is not one of those areas. Need help with a British Car or a guitar? I'm there.
 
  #22  
Old 12-14-10, 04:28 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
SeattlePioneer & Grady--Thanks for the clarification on the pressure switch. I didn't see the hose--it went from the back of the pressure switch straight back to the chamber, and it was obstructed by the switch's mounting bracket.

I hooked up the multimeter to the connectors on the pressure switch. When I turned on the breaker, it jumped to 27.2 VAC for a second or two (system check?), then back to 0.

The purge fan ran, the ignitor glowed, the burners lit, and the blower started. When it flamed out, the pressure switch briefly showed 23.4 VAC. After it restarted, the next flameout showed 27 VAC, and it held there for 3-4 seconds before everything recycled again. I should mention that the voltage jump coincides with the flameout, it does not seem to precede it.

Does this tell you anything?
 
  #23  
Old 12-14-10, 04:41 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
This is a longshot but has it always been windy, particularly a gusty wind, when you have trouble?

For the sake of testing ONLY, once the burners fire, put a jumper across the draft switch terminals. A small wire with alligator clips works well. If the burners still flame out, we have eliminated the draft switch as the source of the probem.
 
  #24  
Old 12-14-10, 04:50 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Grady--I considered the wind as well, but this is happening on still days. Where do I find the draft switch?
 
  #25  
Old 12-14-10, 04:55 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Sorry, it's the switch we've been referring to as the "pressure switch".
 
  #26  
Old 12-14-10, 04:57 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks--I'll try that next.
 
  #27  
Old 12-14-10, 05:05 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
Yay--results! I put a jumper on the draft/pressure switch after it was running, and it ran smoothly for 3 minutes--longest run yet. When I determined that the test was sufficient, I unclipped one of the leads and the furnace IMMEDIATELY flamed out.

Since this determined that the switch is the source of the problem, does that mean with certainty that the switch is faulty? ...or that what the switch is measuring is a problem?
 
  #28  
Old 12-14-10, 05:27 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
Ah-ha, a wise man. Most of our posters would have jumped right on replacing the switch. Now comes the tough part, maybe.

First, you need to get the switch out of the way. Inspect the hose as well as possible. You are looking for cracks, holes, or anything which could cause leakage. If found, replace the hose.
The hose probably connects to a barbed or other push-on fitting at each end. If you can't see what it connects to on the furnace end, don't just pull it out. Just disconnect the switch end. Try cleaning the hose & furnace end with canned air, a piece of wire, etc.
NOTE: DO NOT USE THE ABOVE TECHNIQUE ON THE SWITCH END. Poking anything into the swich or using pressure can & probably will rupture the diaphram. Reassemble, try it, & post back.

S/P, any other suggestions?
 
  #29  
Old 12-14-10, 07:03 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
I checked the hose, and it looks fairly good, if a bit old. I cleaned it out with a length of wire, and didn't feel any obstructions. After checking everything over again, I reconnected and switched on the breaker. The furnace ran nonstop for over 2 minutes (usually doesn't make it that long), and I started packing up the tools, and it flamed out again.
 
  #30  
Old 12-14-10, 07:38 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
You need to measure the voltages on the wires and determine if the pressure switch is opening or something else is shutting off the burners.


This is post #30 and we still haven't determined if the pressure switch is opening.

A good repairman would have gotten that far in about five minutes.

Frankly, I think you need a repairman to deal with your furnace.
 
  #31  
Old 12-14-10, 08:00 PM
H
Member
Thread Starter
Join Date: Sep 2007
Location: USA
Posts: 26
Upvotes: 0
Received 0 Upvotes on 0 Posts
SP--check post #22. I did check the voltage, but I don't know if my test is what you were looking for.
 
  #32  
Old 12-14-10, 08:05 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
Yes, you checked it but what your report doesn't make much sense. You may not have been measuring voltages correctly.


Sorry, but I just don't have confidence this is a line of DIY work for you. I can't trust what you do, and it might take a hundred posts to lead you step by step to a solution ---- and you can't keep track of what's being done or been done in a very long thread.

So I'm outa here. Perhaps others will soldier on. Sorry I can't be of more help.
 
  #33  
Old 12-15-10, 02:54 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
From what you are saying & what you've done, I'm suspecting flakes of rust or something else to be blocking that pressure port. Without having a means of testing, which I have to presume you don't have & would require a draft gauge, sensitive manometer, or magnahelic, we are guessing. Removal of said rust, if that's indeed the problem involves taking the furnace apart to some degree & that requires gasket replacement. Photo #8 shows what looks like a gasket in bad shape anyway. About the only thing left you might be able to do is check the vent pipe/chimney for any kind of blockage. If it goes straight up from the furnace checking could be difficult.
At this point, & I'm not upset or anything of the sort, I think it best to call in a pro. Please keep me up to date on progress.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: