ECM Motor Question

I need some opinions here. MY furnace blower quit tonight. Carrier model 58CVA110 Shows a blower fault. Sure enough the blower rocks but never turns. I pulled the blower out expecting it to be a bad module.

When I checked the resistance on the three wires to the motor windings, I got a strange result. All three coils are about the same resistance (about 5 ohms) but the digital meter bounced all over the place. I even saw some negative resistance readings. I tied down the blower wheel just to make sure I wasn’t generating electricity by moving the blower wheel. I saw resistances from about 2 ohms to about 18 ohms. Every once in a while the negative sign would pop up on my Fluke 116 meter.

I don’t ever remember seeing motor winding resistances that changed. Has anybody else seen this? If so, what did you find was the problem? Was it just the module or was the whole motor bad? I hate to buy a module – then go back to buy a whole motor.

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