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Last year my home's central air condenser fan motor stopped working. When I noticed the house wasn't cooling down I went outside to investigate and found there was a humming sound coming from the unit, but the fan wasn't turning.

After researching the problem online, I found the capacitor may be bad and causing the problem. The capacitor wasn't blown, but I replaced it anyways. The problem still existed; Fan won't spin and a humming sound is coming from the unit.

So, I inferred the motor must be bad. Yesterday I unbolted the fan from the unit to try and spin the blades by hand. To my surprise, it spun. It spun 3 to 5 rotations with a medium amount of force (the same force it would take to bounce a basketball 8 feet in the air). I expected the motor to be stuck and not spin at all, so now I'm second guessing myself.

My question is: How "freely" should it spin? I've read in numerous places that the blade should spin "freely", but I'm not sure what that means. Should it spin around 50 times with a medium amount of force? If I was holding it up in the air, should a 15mph breeze spin the blades like a pinwheel? Or is the 3-5 rotations freely?

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1  
Is that an official NBA basketball filled to regulation PSI? –  Tester101 Apr 3 '12 at 16:23
    
Any update on if a new motor fixed the problem? I'm in a similar situation and am curious as to your results. Also, where did you get the replacement motor from? –  mikeazo Aug 14 '13 at 19:22
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mikeazo, it was the fan motor and it's been running fine ever since. I purchased the motor from Grainger. Make sure you get a capacitor (or capacitors) to match the new motor. –  anthony Aug 24 '13 at 14:52

4 Answers 4

up vote 3 down vote accepted

If you replaced the start capacitor, and you are getting proper voltage to the fan motor than the only thing left is to replace the fan motor. If the fan turns at all without forcing, it should spin when powered up. If the fan turns freely or not is not a definitive indication that is good or bad.

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This. A wire in the armature could have melted, introducing a short or discontinuity that prevents the current in the wire from having the proper electromagnetic pull to move the armature. The commutator could have gone bad (again shorting or opening the circuit). There are several ways an electric motor can fail that leave it spinning relatively freely, and in fact I say it's generally a toss-up between overheating causing the bearings to burn out or the armature to warp (seizing the motor) and these other failures. –  KeithS Apr 3 '12 at 16:32
    
Thanks guys, I'll order a new motor for the unit. –  anthony Apr 4 '12 at 14:33

It should spin freely... I looked at neighbor's condenser fan and they all spin freely with very slight force. However how a motor spins isn't necessarily indicator of whether it works or not. A coil could have shorted or insulation burnt. You can test this by taking an ohmmeter, one lead to the motor leads, and the other to the case. If there's continuity between the leads and the motor casing, it's bad (and in fact sometimes it should blow breakers too). You can also read the resistance of the motor leads, if it's too low then there's a short between the windings.

Basically a good fan should spin at least half a revolution with the amount of force it takes to lift a sheet of paper.

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I'm far from being a HVAC person, but I do like to figure things out on my own. I had the same thing happen and before you order a $300 part, all I did was take it apart and clean it really well. I used graphite lubricant on the blades and 3-in-1 on the shaft of the motor and guess what?!! It puuuurs now ;) Hope this helps.

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Why did you lubricate the blades? They shouldn't be in contact with anything that would cause friction (aside from the air)? –  Johnny Feb 14 at 0:04

if u change the capacitor and does not work turn the power on use a screwdriver and try turning the fan you will notice motor making a buzzing sound and hard to turn just replace motor.I had the same problem and that took care of it.Two more things your motor may have three wire black brown and orange today motor have five wire instruction come with it connect the two extra wire together with a wire nut and wrap it with some electrical tape.Last i recommend u change your contact switch because when your motor start going bad it spark more and more as the motor life coming to an end.I hope this was helpful good luck.

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