Trane XE70 Flame Sensor Removal/Cleaning/Replacement


  #1  
Old 03-20-18, 08:56 AM
M
Member
Thread Starter
Join Date: Mar 2018
Location: USA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Trane XE70 Flame Sensor Removal/Cleaning/Replacement

Trane XE70
Model TUS080A936A1
Mfgrd 10/1988

I have the aforementioned Trane gas furnace. It has an electronic ignition and lately, it's been having some trouble lighting the pilot light and thus the burners. It'll work fine for awhile, but occasionally, it'll fail to light and then stop trying to light. My best guess is that it is going into some sort of safety shutdown mode once it isn't able to light the pilot after a certain period of time. Usually, power-cycling the furnace or reinstalling the thermostat will get it going, but not always. It's getting more and more difficult to get it back working each time it goes. I see a spark and in fact, the sparking will continue long after the pilot light is lit. I suspect that it may be the flame sensor, but am not sure what I can and cannot remove and how.

I had an HVAC technician come out for a $99 checkup. It had been almost 10 yrs since the last one, so I figured I was way overdue. He said everything looked good and that my heating issues were likely due to the flame sensor. He quoted me $450 to replace it. I'm a pretty handy person (Engineer by trade), do a lot of DIY, so I thought I could probably do this one, so I declined the service for now and went to do some research.

The flame sensor is a White-Rodgers 3098-151 3-pin plug-style. After researching, this part is obsolete with no recommended replacement from White-Rodgers. Deciphering the part number of the quote from the HVAC guy, I think that he was going to replace mine with a White-Rodgers 3098-156, even though this doesn't appear to be an approved cross reference. The 3098-156 looks to be in the $150 and up price range. Can anyone shed some light on the differences and what could be an acceptable replacement?

I could attempt to clean it as well, it looks pretty dirty and full of deposits (see pics). Either way, I need to remove it. It doesn't look like it should be too hard to replace, but I'm just not sure what needs to be unscrewed/removed. It looks to be attached to the pilot light assembly. I don't know if the flame sensor is removable on its own, or requires removing the whole assembly, and thus messing with some gas connections (which I'm not sure I'm inclined to do). I've done a lot of looking and, being so old, I can't find any videos or pictures describing how to remove the flame sensor in my particular furnace. Can anyone provide any help here?

Thanks.

--Mark
 
Attached Images      

Last edited by PJmax; 03-20-18 at 10:56 AM. Reason: added pic
  #2  
Old 03-20-18, 10:24 AM
S
Member
Join Date: Feb 2014
Location: USA
Posts: 1,771
Received 0 Upvotes on 0 Posts
$450 ?? that's crazy ! The flame sensor is not your problem. Try cleaning the pilot orifice.
 
  #3  
Old 03-20-18, 10:50 AM
M
Member
Thread Starter
Join Date: Mar 2018
Location: USA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
@skaggsje, that's kind of what I thought on the price too. Is the Pilot orifice the part to the right of the flame sensor? How to clean? Neither of those parts are the most accessible things and I'm not quite sure how to remove them.
 
  #4  
Old 03-20-18, 10:53 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 62,035
Received 3,414 Upvotes on 3,063 Posts
That's a touchy situation.

That's not a standard flame sensor. That uses a mercury bulb connected to a module. It could be a dirty orifice. That flame hood looks to be pretty well rusted thru.

The furnace is 30 years old. Has the heat exchanger been checked for integrity. It may be time to look to a furnace replacement.

I added a labeled picture to your first post.
The orifice is in the red circled part.
 
  #5  
Old 03-27-18, 10:33 AM
M
Member
Thread Starter
Join Date: Mar 2018
Location: USA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks Pete. Sorry I didn't reply sooner, I didn't see a notification of a reply. I had an HVAC Technician out a couple weeks ago to do a general maintenance inspection and to advise on my issue. He didn't note anything wrong except the flame sensor and quoted me $248 for the part, $95 trip charge and $90 labor, $450.67 total. I guess I'd presume he looked at all the important parts, including the heat exchanger, but I didn't watch him like a hawk, nor do I truly know what every part is. I don't recall him taking anything apart, would that be necessary to check the heat exchanger?

Does that whole assembly, including the flame sensor and the orifice, come out as one piece or can the flame sensor come out individually? Can I clean the orifice in place? I'm not inclined to do anything with even the flame sensor if I have to mess with the gas line. I'll leave that to the pros. How can I be sure which part is having an issue though? I'd hate to drop $450 on a flame sensor and find out the technician was guessing and it doesn't fix the problem. Is the orifice and/or flame hood something I should ask the technician to clean while replacing the flame sensor?

I think you're not wrong with it being time for a new furnace, but we are considering selling the house soon and I was hoping to keep it going and let the buyer negotiate with me and make it their choice on how to replace it.
 
  #6  
Old 04-02-18, 10:15 PM
M
Member
Thread Starter
Join Date: Mar 2018
Location: USA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Ok, I think I've figured out my problem. I'll describe in detail in case it helps someone else.

TL;DR, it's fixed, see bottom for 2 follow-up questions.

Today, my furnace finally quite seemingly doing much of anything. No igniter spark. No gas to the pilot. No amount of power cycles, call for heat changes or thermostat resets would fix it. I busted out my multimeter and did some measurements. I verified 24V into the Pilot Relite. I verified 24V at the connector to the Gas Valve by multimeter leads in the connector (more on this in a sec). Maybe not entirely recommended, but I couldn't manually light the pilot because no gas. Natural Gas at my Hot Water Heater and Clothes Dryer was fine. No gas supply issue. I then bypassed my Thermostat and the Igniter started working. Then I noticed the Red wire pin on my Thermostat was loose. I resoldered that pin and the Igniter started working again without bypass. Still no gas. No heat.

Based on the aforementioned diagnostics, my diagnosis was something was still amiss with the Gas Valve. Now I think that the Thermostat thing was my original problem, however during diagnosis, I put multimeter leads into the Gas Valve connector and I think I may have bent the contacts inside 2 of the pins. I revisited this thread that I tried without success awhile back. However this time, knowing 2 of my contacts were probably looser than they should be, I tried more than just small adjustments and finally found a spot where I heard the Gas Valve click open and the pilot light lit. I now have heat, albeit with a screwdriver wedged behind the connector. That'll get me through the night. Oh, and the HVAC guy seems to have been completely in left field with his $450 Flame Sensor quote.

Question 1: During diagnosis, I adjusted the gas flow using the grey screw immediately to the right of the blue gas knob. See picture. I turned it a 1/2 turn counter clockwise. When that did not fix my gas issue, I turned it back clockwise 1/2 turn. I had also talked to an emergency HVAC guy this evening who was very nice, but noted that I should NEVER touch that screw unless I had the proper equipment to adjust it properly. Citing cracking heat exchangers if too high and improper burn/CO2 issues if too low. How sensitive is this gas flow adjustment here and should I get an HVAC Pro to test my gas flow properly? I turned it back to roughly where it was, but I don't know how exact I got it back. It'd probably be another $95 service call, but if I must, I must.

Question 2: I need to replace the connector and/or the wire harness that connects to the Gas Valve. It says F115-0132 on it, see picture, but the Internet comes up empty on this part. Does anyone have any suggestions on a replacement for this?

Thanks in advance for any further advice.


--Mark
 
Attached Images   

Last edited by melview1; 04-02-18 at 10:31 PM.
  #7  
Old 04-03-18, 12:14 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 62,035
Received 3,414 Upvotes on 3,063 Posts
I don't see that plug available from anyone. I went thru the entire W/R parts catalog. You could try a company like in the link and see if they can offer any help.
american hvac parts/p-19263-5-pin-plug-electronic-or-hot-surface-ignition-gas-valve-rheem-trane-white-rodgers.aspx
 
  #8  
Old 04-03-18, 03:21 PM
M
Member
Thread Starter
Join Date: Mar 2018
Location: USA
Posts: 5
Upvotes: 0
Received 0 Upvotes on 0 Posts
Hey Pete,

I couldn't find anything on it either, however I did find this one, F115-0087. Better pictures here. It looks identical to mine, down to the pin configuration and the pre-configured jumper. I don't wonder if it IS the same one, it's just mine is a Trane-specific part number that no longer exists due to the age of the furnace. I had the same issue when researching the Flame Sensor. Mine has a dual-connector (see picture) for each lead connected to the Pilot Relite and then 2 wires go elsewhere, the white to a Honeywell box and the pink/red to a control board (?). If I recall the wiring diagram correctly, each pair of T1 and T2 connections on the Pilot Relite are connected internally too, so I could cut the connectors, leave the wires that go elsewhere, then replace the 2 that I need to with the new wiring harness and connect it to the Gas Valve. Does this sound just crazy enough that it just might work? For $13 it probably can't hurt to try?


--Mark
 
Attached Images   
 

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