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Gaust

AC Fan or Capacitor?

7 posts in this topic

Hello,  I have an Arcoaire outdoor AC compressor that the fan motor quit running.  I dug out my DMM, pulled the service panel, and tested for power.  I have extensive DC experience but not much AC.  The contactor works fine, there's power to the fan run capacitor and power out from the capacitor to the motor.  I unplugged the motor and tested for power on all 3 leads and got 120volts on each.  The fan blades turn freely, they don't feel like they are bound up.  It appears to me that the motor needs to be replaced but I thought I'd ask for a second opinion before I purchased a new one. 

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Need appliance parts? Call 877-803-7957 now!

If the cap looks the least bit  "swollen" it's probably bad.  You can pick up a multimeter with a cap checker function at radio shack.

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I forgot to mention that the cap appears fine.  I have seen bad caps before and I don't see any  swelling or bulging at all.  I guess I can pick up a cap checker just to make sure.  Thanks

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Hello

When U pulled the plug off the mtr did you check the voltage across the wires? If U did then U should have read 208VAC across the wires and 115VAC from each wire to GRD. I,m kinda assuming this is the condender section(outside) and main power to it is 208-1 ph- 60 cycle

Normally a condenser fan mtr is wired this way: one motor lead goes to the compressor contactor(or some relay contact). Thats one power wire (L1) out 2 the mtr. Another motor lead will go 2 one connector of the cap. They'll also be another power wire on that connector(L2). The 3rd lead of the mtr goes to the leaving side(charging) connector of the cap and it should be the only wire on that connector. Some manufactures do do it differentl. B :poison: careful. This is going to be line voltage.

Set the unit 2 call 4 cooling but disconnect the wires at the fan mtr( if possible).  Ur going to have to act a little fast to do this or U could take 1 reading, shut the unit off and then start it again to take the 2nd reading.

Use your meter and take a reading across the L1 & L2 wires(normally the black & white wires) U should get 208VAC. Take a reading from L1 to the other mtr lead(normally a brown wire) U should get 208VAC, possibly alittle higher. If U get the above readings then all is well with the unit, but UR fan mtr is defective.

If U can't disconnect the wires @ the mtr then remove them from there contact points in the electrical panel and make a diagram so U put them back right. Take the readings @ the contact points.

Hope this helps:)

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[user=10641]Gaust[/user] wrote:

Hello, I have an Arcoaire outdoor AC compressor that the fan motor quit running. I dug out my DMM, pulled the service panel, and tested for power. I have extensive DC experience but not much AC. The contactor works fine, there's power to the fan run capacitor and power out from the capacitor to the motor. I unplugged the motor and tested for power on all 3 leads and got 120volts on each. The fan blades turn freely, they don't feel like they are bound up. It appears to me that the motor needs to be replaced but I thought I'd ask for a second opinion before I purchased a new one.

I have a little problem here. There should be zero voltage on one of the power leads like the ground side of the supply line?

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the cheapest way and simplest way to check a condenser motor is to buy a little cap thats the same MFDs as the motor, 5 mike, of 7.5 or whatever and connect the cap to the purple common (or white) and the brown wire and apply 220 volts to the motor between the black wire and the purple (or white) common wires and take an amp draw reading with a clamp-on while the dang thang is running, this is what I do

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