XL90 Gas Furnace will not start

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  #1  
Old 11-04-10, 10:23 AM
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XL90 Gas Furnace will not start

Tried turning on heat for first time this year, nothing. Red light flashes 3 times indicating Inducer Error. Inducer blower does not even try to come on. I have turned power off for several hours and re-tried, but same error. I also replaced the main control board 2-3 years ago. The original control board had intermittent problems with turning on heat, since the board has been replaced I have not had any further problems. I put the old board back in today and got the same Inducer Error code so I am pretty confident the control board is OK. Have not had any problem with the AC this summer either. Is it common for the Inducer Blower Motor to completely go out? Heat worked all through last winter. Is there something else to look for or test before replacing inducer? Thanks in advance for any help.

Mark
 
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  #2  
Old 11-04-10, 11:18 AM
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I'd use an AC voltmeter to verify that you have 24 VAC on the W contact in the furnace verifying that the thermostat is calling for heat and the circuit board should be turning on the inducer motor.

Then disconnect the inducer motor and see if you have 120 VAC coming from the circuit board to power up the motor. If you do, you have a bad inducer motor. If you don't a bad circuit board.
 
  #3  
Old 11-04-10, 12:11 PM
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Thanks for the reply. I get the rapid flashing indicating that the thermostat is calling for heat, then it goes to 3 slow flashes indicationg inducer error, but I will check for 24V to be sure. I plan to look at after work today and planned on checking for voltage to the blower motor, just wasn't sure if there was a relay or fuse that I should look for also. Thanks again for the reply, I will post my findings.
 
  #4  
Old 11-04-10, 01:38 PM
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XL90 Inducer Error

Quick question, which contacts are used for checking for 24V? Thanks for the help.
 
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Old 11-04-10, 02:26 PM
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Make one connection to the furnace chassis ground and use the other to test for voltage.


The pressure switch may be two contacts (SPST) or three connections (SPDT) with the common contact supplying 24 VAC to the switch.
 
  #6  
Old 11-04-10, 02:54 PM
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Thanks so much for your assistance. I am having trouble getting the 24V reading, not sure if I'm grounding correctly. But, I do get AC Voltage going to the inducer motor, it started off low than gradually increased to around 118V but the motor will not come on. I would assume the motor should start as long as it is receiving voltage, but just not sure if something else could be keeping it from starting. There is an ECM Motor mounted to the inducer motor also, could there be anything controlling the inducer motor in the ECM? What exactly does the ECM Motor do? I would assume it detects the speed of the inducer, but there are 9 or so wires coming out of it, so it must be doing a lot more. Thanks again for your help.
 
  #7  
Old 11-04-10, 03:34 PM
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Update

You did say 24AC, I was checking for DC!!. Got it, checks good, also getting 120VAC to inducer motor. I will contact HVAC parts supplier tomorrow and see what they say about the inducer motor. I guess the ECM Motor is all related to variable speed motors. Looks like I have a bad inducer motor. Thanks again for your help.
 
  #8  
Old 11-04-10, 04:32 PM
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OK, still a little confused. After taking motor off, I disassembled the housing...the wires sending 120V to the motor do not go anywhere. They dead end into a round connector and is screwwed onto the outside of the plastic housing. Therefore, the motor must be controlled by the wires going to the ECM Motor. Anyone have any information on checking to see if the ECM Motor is bad?
Part# on the plastic housing is Customer P/N X38040336020 & No. 7000-5838.
Part# on ECM Housing is Cust pn 8767-4220 & 5SME44JG2002E.

Any help is appreciated.

Mark
 
  #9  
Old 11-07-10, 07:00 PM
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That is a variable speed inducer motor. I don't have my book here to tell you the procedure for testing the motor. I am a Trane tech and have seen many of those motors go out. I understand Trane has discontinued that motor and now sells a kit to upgrade to the round variable speed inducer motor. I did a google and see one from another company for $500. The upgrade kit could cost as much as $1000 to get it installed. It comes with new inducer motor, control board and complete wire harness. I have two used inducer motors for your furnace. I am listing them on ebay, let me know if you're interested.
 
  #10  
Old 11-08-10, 05:27 AM
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Thanks for the reply. I was told by a local Trane parts house $700+ for the new motor kit and wiring harness, ouch! I can find original motor online for around $400, will probably go that route. I am going to contact a local electric motor repair shop today and see if they can help test it. I just want to know for sure it is bad before spending anymore $$. I will look for your ebay listings as well.
 
  #11  
Old 11-08-10, 06:29 AM
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I can't help with your problem, but I have a question for you.
Where are you getting your Trane parts?
I am thinking about buying a Trane this year and am thinking about parts. When I tried to get replacement parts for my current furnace, I had a real hard time finding a local place that sold furnace parts. I ended up getting several things off the internet. Is that easy to do with trane parts, too?
 
  #12  
Old 11-08-10, 07:08 AM
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I think it's difficult to find parts for a DIY for most all brands, and understandably so due to the safety involved. I just drove to a parts house that most local distributors use because I needed the part ASAP. You can find parts on-line a little cheaper if you know the exact part number you need. Not much information available for cross referencing, troubleshooting, etc. Trane appears to be very good at keeping it private.
I have been completely unhappy with my Trane since it was installed(new construction), have always had issues with the inducer blower motor error and had to call the installer back almost every year. I could reset it myself by cutting the power, and usually did since it was cold, but I wanted them to know there was a problem so I had them come out each time. Always some story about blocked drain lines or a leaf blocking the air intake, but I knew they were just making excuses. They did replace the heat exchanger due to a recall, but it has a lifetime warranty on it. Once the warranty ran out the main board failed and they would not cover under warranty even with all my previous problems. I ended up replacing it myself and have not had any problems for the last 2-3 years until now. Now I have discovered that there is a replacement kit for my main board and inducer motor due to a defective design. I have been telling them that for the last 9 years! No way I would ever buy another Trane unless my research showed that they were definitely the best, which I doubt it would. Just my opinion, but I don't think they stood behind my piece of junk and I will not spend any more $$ with them once I am done with this unit. Good luck with your choice.
 
  #13  
Old 11-10-10, 04:57 PM
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Trane is not one of the furnaces I am as used to working on. If yours has the electronic motor that is variable or multi-speed, it would make sense to me that more could go wrong, not just with that, but with the board(s) controlling it - and also the safety circuit - to detect any anomolies in the various stages of operation. A prime spot to test would be at any of the pressure switches when the failure occurs.
 
  #14  
Old 11-11-10, 10:30 AM
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Thanks for everyone's suggestions. I replaced the main board because it had gone out before and the symptoms were the same this time, but still had the same problem. Found a used ecm inducer blower motor and all is working well for now. I have a spare control board (CNT2871) if anyone is interested, I will make you a good deal. It's only been used one time, I put the 2nd original back in.

Would still like to know the official troubleshooting procedure to determine whether the board or ecm inducer motor is bad. Very difficult to find this information, if I knew how to test the motor it would have saved me a couple hundred dollars. I know the motor was getting 120V supplied to it, but not sure if it must also receive some signal from one or more of the other ten or so connections. If anyone has this information and would be willing to offer it up, it might be helpful in the future.

Thanks again for all of the suggestions.
 
  #15  
Old 11-11-10, 04:16 PM
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I would like to start off by saying Trane is hands down top of the line equipement. I have worked pretty much on it all and there are many things that make it one of the best. Unfortunately I have seen many bad installs that give the equipement a bad reputation. I have seen this with all brands. Installs not done properly lead people that don't know any better to blame the equipement instead. Blocked drains and leafs in the pipes can set off pressure switch errors with any brand. I have personally went out in the middle of the night to clean out a leaf. Bugs have been known to block drain lines causing water to back up and let the pressure switch suck up water and stop the switch from working. If you have had consistent problems with a pressure switch error, maybe the PVC pipes aren't sized properly. Or maybe they are too long and/or too many elbows. If they used a termination kit on the outside maybe it is installed backwards. Any furnace 100,000 BTU or more require 3" PVC vents and not 2 inch. I could supply the information on testing the ecm motor. You have my email because I have emailed you information but have not heard back from you. Send me an email so I know you check it and I will email you a copy of the pages out of my book for testing. As far as parts for Trane go, you do have to be a dealer to buy from Trane. Main reason being they don't want any Joe-Smoe out there installing parts. We spend many hours every year taking training classes so we know what we are doing. Let's face it, Trane has some to the best warranties for parts so they are kind of picky about who is changing parts out. They need the stuff fixed properly not a bunch of parts changers out there.
 
  #16  
Old 11-11-10, 06:55 PM
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How funny.

I just had my furnace repair man here today to look at mine because it'd work one minute and then not the next. The inducer motor would be on but no flame. He checking the vacuum and it was -.35 and it is supposed to be about -1.5. So he removed the inducer to make sure there wasn't something blocking it. He plugged it in while it was in his hand and turned the furnace back on. The motor turned on and to his surprise the burners lit too!! He about fell over. There was no pressure in the system to close the pressure switches yet it ignited. He contacted Trane tech support and they told him the Inducer is telling the control board the pressure switches are closed so I need to install the expensive kit. They also said not to run the furnace because it could start on fire if the Inducer stopped working completely. The price for the kit is $525 and about $150 for labor to install.

I contacted Trane to see if they could do anything for me as the furnace is only 8 years old and to me the inducer is a poor design. Very unsafe design. I was told to go pound sand. Now I'm stuck deciding if I want to spend the $700 to fix this furnace or buy a different manufacturer for $2800.
 
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Old 11-11-10, 10:51 PM
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Here's the rare repairman who uses a manometer right off the bat to correctly diagnose a venting problem! How rare it is to find someone doing the right thing rather than charging someone $200 to replace a pressure switch that isn't the problem.

I surely don't understand the advice the guy got from Trane, though. I'm not saying it's wrong, I'm just saying I don't understand it.

The repairman gets four stars (****) for doing an honest and competent job so far!

Still to be determined ---- why is the negative pressure so low? !
 
  #18  
Old 11-12-10, 03:54 AM
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Not sure what he may have done to cause that furnace to light. It is near impossible to do what you discribed. When that motor first starts, it not only looks for the pressure switch to close. It makes sure the switch is operating by slowing down until the switch opens and then speeds back up till it closes again. Your low pressure to start tells me the motor isn't getting up to the proper RPM or there could be an obstruction somewhere in the piping, drains, ect. The poor design is not Tranes fault, they didn't make that motor. They only used what was supposed to be a good product. When you made your purchase, you should have been offered a chance to purchase the 10 year parts and labor warranty. Yes, it cost extra but it sure would be nice to have to get this kit installed. I have installed about two dozen kits so far under peoples 10 year P&L warranty.
 

Last edited by toppytop; 11-12-10 at 05:48 AM.
  #19  
Old 11-12-10, 06:25 AM
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toppytop,

Thanks for your explanation of how the inducer motor/pressure switch work. That's a new one on me.

I don't suppose the bad pressure read could be the inducer motor slowing down to cause the pressure switch to open and not speeding up again?

Is there a way to know whether that test is in the process of being performed?
 
  #20  
Old 11-12-10, 03:33 PM
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It actually performs this after the flame has lit. It also does this to tune the speed to optimal RPM. If you are not setting the pressure switch prior to ignition, I would suspect a vent piping issue or drain problem. Pull the hose off the front of the flue box that goes to the pressure switch. Gently suck on the end of the hose and see if there is any water in the pressure switch. Small birds and mice have been found inside the inducer housing (had a bird this week). Pull your exhaust out of the top of the furnace and look down inside. You can hear the test and tune once the furnace fires. You will hear the motor step down in RPM until you hear the click of the pressure switch open (listen carefully). Then it will step back up until it closes and will stay at that speed. It does this again for second stage. There is a chance the motor isn't speeding up enough to set the switch to begin with. When a call for heat arrives, the inducer starts and will run up in RPM until the switch closes for the first time. If it doesn't close, the motor will ramp up to full RPM for several seconds to try and set the switch and then trip the pressure switch error if the switch never sets.
 
  #21  
Old 12-01-10, 03:21 PM
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Well I was sitting there watching him and as I mentioned, all he did is remove the motor and plug it back in and the flame lit! He was blown away.

First house I've built. I guess one just wouldn't think something could go wrong with a 8 year furnace that would end up costing you $800. Seems extreme to me. I'll buy a carrier next time! lol. :-)
 
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