Need help wiring in new oil furnace blower motor.


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Old 03-13-09, 12:00 PM
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Need help wiring in new oil furnace blower motor.

I have an old Sears oil fired counter-flow furnace, model number 867.741310, in which the original blower motor went bad (bushings worn out). I went to our local Cashwell's Appliance Parts & purchased a replacement motor. They sold me a Fasco p/n D727 1/3 hp 115v motor. I installed the new motor & now: Blower comes on right away when you turn up t-stat but it shguts off as soon as the burner shuts off, instead of running a little longer to cool off the burner. When this happens, you can hear the motor humming. Also, the only other issue is that the manual/auto circulator switch on the unit itself will not start the blower & the same hum occurs. The old motor had 5 wires: brown to capacitor, black to hi on connection board which also has a jumper to the other side of capacitor, blue to med on board & red to low on board which also has a yellow lead going to the fan & limit switches. The new motor has 6 wires: brown-cap., brown/white-5mfd370vac (was told by supplier this wire would not be used-just cap it), white-common/line, black-hi, blue-med, red-low & grn/yel to case ground. I have the new motor wired like this: white-neutral/line, brown-cap., black-hi, (with jumper still in place to other side of cap., blue-med, red-lo, (with yellow lead still in place to fan & limit switches. When testing the unit I find 115v on the red (lo) wire when you switch on the circulator switch to manual (if you manually spin the blower wheel, the fan will slowly start up). Please help.
 
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Old 03-13-09, 03:22 PM
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Fan motor wiring

Is the cap new & right for the new motor?
Sounds like your motor is wired wrong.
Brown goes to one side of the cap.
Brown/White to the other side of the cap.
Black-High
Blue-Medium
Red-Low
White-Line Common
Green/Yellow-Ground
Remove the jumper from Black (High) to the cap
 
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Old 03-13-09, 07:33 PM
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Grady, thanks for the info; I won't be able to switch connections until tomorrow. I have a perfect diagram for the OE Sears system which plainly shows black/line going to fan limit switch, then coming out yellow & attaching to the blower connection board @ the red low speed terminal. It also plainly shows a black jumper from the hi speed terminal on the blower terminal board to the capacitor, oppossite of the brown wire. The new motor also has the wire colors & their purpose. If need be, I can upload o0r fax the schematics to you. Thanks again for your help
 
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Old 03-13-09, 07:38 PM
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Oh, by the way, the capacitor was purchased new w/the motor.
 
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Old 03-14-09, 11:38 AM
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Wiring Diagram

The old motor may have worked fine that way but I don't believe the new one will. Try it my way.
 
 

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