TblShoot 2 Speed Range Hood Fan

jerry_njMarch 10, 2013

My kitchen range hood fan no longer works - it is about 2 years old and has seen only light use. Here is what I believe is the replacement fan:
Broan Replacement Range Hood Fan Motor and Fan - 2 Speed # 97012248, 1.1 amps, 120 volts - nutone Broan

I would like to first verify the existing fan, not switch/wiring is the problem. I pulled the fan it has a three wire connector. The wires are colors Red, Black and White.

Using an ohm meter I measure about 6 ohms between Red and Black. I read an open between Red/Whit and Black/White. All three measure open to the metal lament. As the fan does not work in either speed I'd guess the White wire is open inside the fan unit. Or, the Red to White would be low, say, and that plus the Black to White would be the second/high speed. That works for me logically, but I do not know anything specifically about this motor, or even this type motor.

Seeking advice on what I should measure with a DC Ohm Meter between the three named wires.

Or does the White being open to both Black and Red tell me the motor is bad?

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Okay, I looked on the web and found a diagram for a Single Phase 2 Speed electric motor.

It shows a center off rocker switch with the Phase (hot) line coming to the switch. In one (side) position it connects the Hot to the red and in the other to the black, both return via the white to the neutral. Thus, if the return/white is broken (in the subject motor somewhere inside the motor) one would read a resistance between red and black, and an open between white and either of the the other two.

    Bookmark   March 11, 2013 at 10:37AM
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Typically, two-speed appliance motors use a white for neutral, red for low, and black for high.

As long as you are comfortable doing this, use a zip cord with a plug on it, stripped at the other end and attached with wire nuts to each combination.

If I'm checking an unknown motor, I usually will plug it into a power strip with it's own breaker in case there is a fault in the motor - it will usually trip faster and with less smoke. :)

    Bookmark   March 11, 2013 at 11:33PM
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Thanks that fits with my thinking/analysis and web findings. I had not interpreted far enough to determine which color was which speed.

I think your test method would work well. I sometimes put a low resistance, maybe a 200 watt bulb (or 1 ohm high wattage resister) in series with such a test arrangement, then if the motor, say, is shorted the light will light and the current will be limited to less than 2 amps for 120 volts.

I decided based on my ohm meter reading to order a replacement fan. Some one told me they had seen a not replaceable thermal or current (fuse) under the wrap in the white return that was blown/burned out. I started to cut into the wrap but quit as it looked like I might cut some wires in the coil that would further damage the unit. I will hold on it for a while in case my interest increases enough to tear into the motor.

    Bookmark   March 14, 2013 at 2:06PM
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