More Info on ECM Motors

The other day, a service tech called and wanted to make sure that he was making a COMPLETE diagnostic of an ECM motor that was not working.  He had checked out the motor with his GE TechMATE Pro and found the motor would not run.  He had taken off the module and checked out the motor with both the “ohms” test to the shell and between “windings” and the motor was good (see ECM Motor Troubleshooting post Part 1).  He knew he had a bad module.

But he also wanted to make sure the unit control board was good and sending the correct signals.  He had the “decoder chart” for the pins that was on my troubleshooting post EXCEPT the 16 pin plug only had 12 wires in it.  So he was  lost  but still wanted to make a complete diagnostic so he called me.

Believe it or not — I didn’t have the answer!   It seems some manufactures have, over the years, modified the basic wiring to suit their particular application. So I made a few phone calls and found out a couple of things.

On motors using the 12 wire application instead of all 16 wires, the manufacturer was “doubling up” the duty of some of the connectors. Attached below is a chart showing how the pins were doubled up.  We were still able to verify some of the pins like position 15  – “G” – with just the fan running and position 12 – “R” – as power to the module, so we were pretty sure the board was functioning properly.

ECM pins 2

After I had obtained this info, I passed it on to the tech and he finished his check out of the board when he went back with the new module for the motor.  The board did turn out to be GOOD still .

Now, in the process of doing all this research, I learned one more thing: that some manufacturers REVERSE W1 and W2 in the plug and programming. Regal-Beloit uses a “standard” configuration for the plug but manufacturer’s can modify to suit their needs to a point.  Attached is the Regal-Beloit chart showing their default pin positions.


Original pin position diagram from original post:


ECM 16 pin plug layout

Note that position 2 is W2 and position 13 is W1 above but  the Regal Beloit standard is position 2 is W/W1 and position 13 is EM/W2(EM = Emergency Heat).  Note: the original chart in my post had it the opposite. This is another good reason to ALWAYS follow the manufacturer’s instructions/wiring diagrams as that original post had the chart  taken from a York manual.

Well, today was a very good day for me because I LEARNED 2 new things!  Hopefully, this post will help you further in your diagnostics. All of this came about because a CONSCIENCIOUS SERVICE TECH wanted to do a complete job. — My hat is off to him!

Thanks to the Regal-Beloit Dealer Tool Box site for the “default position” chart information above.  Also — Thanks to Casey McConnaughy of York Tech Service for the 12/16 pin position information.


About yorkcentraltechtalk

I have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners. For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired. One of my goals has always been to "educate" dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it. The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way. I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about. Thanks for taking the time to read my postings! Mike Bishop
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3 Responses to More Info on ECM Motors

  1. dsomerv says:

    Very enlightening … thanks
    (spell check: CONSCIENCIOUS 😉

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