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  1. #1
    Join Date
    Nov 2008
    Location
    Northern California, foothills.
    Posts
    212

    ECM Inducer Draft Motor Troubleshooting.

    I am generally confident going on gas heating service calls, but one
    thing (of a few) that I am fearful of encountering is a problem with
    an ECM inducer draft motor. I've seen them on units, but they
    have always thankfully worked.

    Can those of you that have encountered issues spill every helpful
    thing you know about them? The main goal, I suppose, is to
    distinguish between issues with the main furnace control board
    and the controller on the motor?

    Thank you.

  2. #2
    Join Date
    Apr 2004
    Location
    MN
    Posts
    1,800


    Sorry george, no answer here. But sit down and I'll share a beer with you while waiting for responses. I've never had to diagnose one either.
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  3. #3
    Join Date
    Feb 2006
    Location
    USA
    Posts
    4,381
    I've never seen one either do they sell some sort of tester i wonder to cover all types

  4. #4
    Join Date
    Mar 2010
    Location
    Kent, WA.
    Posts
    188
    zebra instruments has a ECM motor testor im seriously considering buying. on the commercial side of things im seeing a lot more equipment with ECM motors in them. I did a startup of a trane 10 ton package unit. It had a backwards inclined direct drive ECM motor for the blower. you set the cfm via a dc output board in the blower compartment since this was a CV system. the outdoor condenser motor was an ecm for head pressure control.

    http://www.getzebra.com/proddetail.asp?prod=VZ%2D7
    Experience
    Is what you get when you didn't get what you wanted.

    A positive attidude will not solve all your problems, but it will annoy enough people to make it worthwhile.

  5. #5
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    511
    There are a variety out there. The ones (true ECM) that you may be refering to have the black 'box' mounted to the inducer assembly. I saw them alot of trane/american standard 'freedom' units. There where two generations of these; one mounted verticaly while the other mounted horizontal. A problem was that the wiring harness would never reach, when retrofitting a gen 2 to a gen 1. I recently took the time to walk a guy through the trouble shooting process on one of these inducers. The 'head' or black box was the problem. According to this tech, when he went to get it, he was informed that the motor head and inducer assembly all came as a single unit at that there was no real need to diagnose because you'll be replacing the entire assembly anyway. That being said, the troubleshoot is not difficult and requires about 3 DC volt readings. I have a guide that i can share if you're intersted.

  6. #6
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,021
    Quote Originally Posted by ADillon View Post
    There are a variety out there. The ones (true ECM) that you may be refering to have the black 'box' mounted to the inducer assembly. I saw them alot of trane/american standard 'freedom' units. There where two generations of these; one mounted verticaly while the other mounted horizontal. A problem was that the wiring harness would never reach, when retrofitting a gen 2 to a gen 1. I recently took the time to walk a guy through the trouble shooting process on one of these inducers. The 'head' or black box was the problem. According to this tech, when he went to get it, he was informed that the motor head and inducer assembly all came as a single unit at that there was no real need to diagnose because you'll be replacing the entire assembly anyway. That being said, the troubleshoot is not difficult and requires about 3 DC volt readings. I have a guide that i can share if you're intersted.
    IMO pretty much covers it.

    ECM (true variable speed) motors are easy to diagnose:

    Power off first...
    Disconnect motor from controller and check windings for opens or grounds
    If above checks, then the problem is usually a bad module

    I have only seen a few, and only one bad one... and yes it was a Trane and yes I had to buy the motor/module kit.

    I hear Goodman/Amana uses them on their MOD furnace, have not worked on one yet.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

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  7. #7
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    511
    I did hear that other manufatures where using them, but i haven't seen any either. Most 'variable speed' inducers these days are actually just a/c motors which have the voltage to them varied by the board. These are much easier to diagnose. Tec-mate pro works for blower drives but not inducers. I have a tech-mate and have never had to use it. Every VS failure has been in the commutator(power head) and has been obvious by both smell asnd sight (I have seen the same resistor burned out in at least a dozen blower drives) this is always nice because you don't even have to remove the motor from the blower assembly to replace the head. The method you described is perfect for determining motor vs power head failure. There is sometimes the need to determine whether the failure is in the IFC board of the 'head' this canbe done with a dc volt meter and just a couple of readings. I have yet to see a VS failure that was not the commutator/head. Has anyone seen an actual motor or control board failure?

  8. #8
    Join Date
    Sep 2003
    Posts
    1,675
    Not to hijack the op thread but I had a ecm motor failure on an 11 year old Bryant
    2 stage 80 percenter. Also some jackleg installed a taller water heater than he liner would allow and pushed down the Diverter onto the WH and screwed it into place.

    Motor and head too expensive to replace

    Ended up replacing the furnace and replacing the water heater diverter.

    Also I haven't seen a defective ecm inducer motor but carrier/Bryant has a ecm motor simulator for some of it's furnaces

  9. #9
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    511
    Yes, it is an expensive assembly.

  10. #10
    Join Date
    Apr 2004
    Location
    MN
    Posts
    1,800
    So what readings am I (and the OP) looking for to determine if the problem lies in the "head" or the IFC?
    A Veteran is a person, who at some point in their life, wrote a blank check payable to the United States of America for payment up to and including their life.
    Gene Castagnetti-Director of the National Memorial Cemetery of the Pacific in Hawaii

  11. #11
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    511
    first off there is a tester for these motors. but i don't know it's name. it is reffered to as the VS trouble in this manual.

    manual method for testing VS inducer:

    1) Ensure that the IFC is powered. all checks are made with plug in place @ board and power on.

    2)check for dc voltage between pins 2&3 of the plug, at the board going to the VS inducer. 13v dc should be present. if not - replace IFC (ensure power to IFC)

    3) place jumper between pins 3 & 4 on the molex plug. if the motor starts, continue to next step. if the motor does not start: ensure that the pressure switch is in the open position. either with meter or by removing wire from the switch. If the pressure switch is in the open position and the motor will not start then replace the motor & head. if the pressure switch was stuck closed, then you have found the problem; the switch was stuck closed.

    4)the motor started. once the pressure switch has closed then opened and then closed again, remove the jumper from pin 4 and move it to pin 5. keep the other end of the jumper on pin 3. if the motor stops then you where to slow and you must repeat the steps. if the motor goes into high speed: replace the IFC. If the motor does not go into high speed: replace the motor & head.

    Checks should be done 2x to ensure accuracy

    pins from top to bottom

    1
    2
    3
    4
    5

    hope this helps. Hopefully you will never have to use it.

  12. #12
    Join Date
    Mar 2012
    Location
    West Chester, PA
    Posts
    511
    because the motor and head are replaced together, there is no need to determine if it is the commutator head or the motor but FYI the motor windings may be ohmed and should all match (3 phase style) if they are open, shorted or do not match it was the motor. If they are in tact then the commutator/head was the problem. It doesn't really matter because they come as a single, expensive piece.

  13. #13
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,836
    Quote Originally Posted by small change View Post
    Not to hijack the op thread but I had a ecm motor failure on an 11 year old Bryant
    2 stage 80 percenter. Also some jackleg installed a taller water heater than he liner would allow and pushed down the Diverter onto the WH and screwed it into place.

    Motor and head too expensive to replace

    Ended up replacing the furnace and replacing the water heater diverter.

    Also I haven't seen a defective ecm inducer motor but carrier/Bryant has a ecm motor simulator for some of it's furnaces
    removing the draft diverter may have been a better thing for that water heater.

    If you remove the draft "diverter", you divert the draft back to the water heater where it belongs.

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