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I bought a direct replacement blower for my furnace but when it arrived I noticed two wires were crossed. the original motor has a red, white, and black wire in the connector. The new one has a fourth (blue) wire and it is in the slot where the black wire is on the old motor. Would it be safe to assume that this blue wire can be removed and the black wire moved into the same spot without causing problems? The old motor had a green wire connected from motor chassis to fan housing.


I managed to find a photo of the old motor and found an image of the replacement online. Hope this helps, thanks for all the help.

Old and New motor

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    Do the blower motors have stickers with wiring diagrams on them? If so, take pictures of both and post them here. Also, model and part numbers would be helpful. – longneck Apr 16 '15 at 19:56
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    There is no guarantee that both motors use the same color coding. – Brad Gilbert Apr 19 '15 at 1:37
  • longneck, sorry for the delay was out of town. Unfortunately I have only one photo of the old motor showing the wiring schematic. If the new one has one, I will get a pix and post it. It will be this weekend at the earliest seeing that the furnace is at our vacation spot some 3+ hours from home. – Rudy Apr 20 '15 at 19:43
  • @longneck, I managed to find a photo of the old motor and found an image of the replacement online. Hope this helps, thanks for all the help. [Old and New motor][1] [1]: i.stack.imgur.com/Eu0sG.jpg – Rudy Apr 22 '15 at 13:34
  • @longneck, turns out it was just a matter of what speed you prefer. Black is high and Blue is Medium, worked out well. – Rudy Apr 27 '15 at 20:24
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Yes you are correct. That will increase your fan speed a little in cooling or fan only mode. The white wire is the common the colored wires are the speed taps. Black is high, red is low and blue is medium. Cap one of the colored wires and use the other two. Usually the black is for cooling and the red is for heating but having the 3 wires gives you options for the fan speed. If you are unsure if there is enough air to cool the furnace properly use the highest speed. The brown wires are for the capacitor which must be replaced at the same time with the matching micro farad rating as the motor.

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