Outside Central Air Unit Locking Up


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Old 08-22-14, 06:14 AM
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Angry Outside Central Air Unit Locking Up

My central air unit fan is locking up like the motor is frozen. I took some other advise and replaced the capacitor and when I did it took off like brand new but shortly after it "locked up" again. When the power is applied it is like the motor is seized up as it is hard to spin it but when the power is off the motor spins with ease.

I am thinking at this point I have to replace the motor? Any other suggestions that I may be missing?
 
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Old 08-22-14, 06:35 AM
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Post the microfarad value of the capacitor that you replaced.

Do you have a multimeter that measures ohms?
You can turn off power and isolate the motor wires to take an ohm reading between the 3 wires to the fan motor and post this information.

Com to run = the lowest reading.
Common to start = a higher reading.
Start to Run = the sum of your other 2 readings.

If you have 2 brown wire don't measure the brown with a white stripe.
Brown is usually start.
Black is usually common
Run varies by brand of unit. (Yellow with Carrier)
Refer to the wiring diagram.
 
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Old 08-23-14, 09:47 AM
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No I do not have multimeter unfortunately. I know the capacitor I have is the correct one as I took the old one to the electronics shop and matched them up. Are you thinking that it could be something else besides the fan motor?
 
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Old 08-23-14, 10:22 AM
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If you replaced a 45 microfarad capacitor or a 227 microfarad capacitor you replaced the wrong capacitor.
 
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Old 08-23-14, 10:45 AM
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Both the old and the new are 5+35uf/370VAC 60HZ
 
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Old 08-23-14, 10:49 AM
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Check the fan motor as mentioned. go get a multi-meter.
 
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Old 08-23-14, 12:40 PM
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If you have a Harbor Freight near you, you can pick up one for
 
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Old 08-23-14, 01:36 PM
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I am just wondering, is their something else you all are thinking could be the problem? Keep in mind I already replaced the capacitor.
 
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Old 08-23-14, 04:14 PM
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Open windings.

 
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Old 08-24-14, 10:06 AM
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Thanks Houston but I am not sure what I am looking at. Here is a picture of my setup. Right now it seems that if I turn on the air after a long while of not using it the fan will spin no problem for awhile and then lock up. Then if I turn it off and back on it will not spin at all until I wait some time and try again

Name:  IMG_20140824_120405569.jpg
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Old 08-24-14, 10:26 AM
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2 of the wires on the capacitor and 1 of the black wires on the bottom of the contactor run to your fan motor.

I turn off power, wait 2 minutes, manually push in the contactor for a few seconds (if the stat isn't already pulling in the contactor), grab a wire with 1 hand and and push it in and out of the "firewall" while looking down the top of the condenser to identify the 3 wires to the fan motor.

Unplug the 3 wires and measure the resistance between them.
The wire on "Fan" on the dual capacitor is start.
The black wire on the contactor is common.
The remaining wire between the fan and "Com" on the dual capacitor is Run.
 
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Old 08-24-14, 11:07 AM
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I will get a tester on Monday but is there really anything else it could be aside from the fan motor? I do not see any other parts aside from the capacitor and fan motor.
 
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Old 08-24-14, 11:47 AM
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You're right, other than the contactor (which switches power to both the compressor & fan motor), the fan motor and capacitor are the only other devices in the fan circuit. From your description of the problem (runs for awhile then stops and won't restart until it cools off), I'm guessing you may have a shorted winding in the motor, causing it to overheat. When it gets to a certain temperature, the thermal overload protection kicks in, turning off the motor. It remains off until it cools down enough for the thermal overload protection to kick out, allowing the motor to operate again.
 
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Old 08-24-14, 12:06 PM
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The dual capacitor appears to be incorrectly wired.
Brown from the fan motor should be the only wire connected to the "Fan" terminal on the dual capacitor with most brands.
It appears that your brown is sharing a post with a white wire.

If you post a clear shot of the wire connections on the dual cap and a shot of your diagram we may be able to verify this.

You could also just type the connections and post a pic of your diagram on the panel over your control box:
Fan: ?, ?
Herm: ?,?
Com: ?, ?
 
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Old 08-24-14, 12:30 PM
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I am not sure it has anything to do with cooling because it has been a couple hours and will not kick on, the motor acks like it wants to go and the unit shakes but the fan does not spin. Seems more hit and miss I guess than amount of time lapsed.

Here is a picture of the capacitor, I am fairly sure the wires are in the correct place as I took a picture of the old capacitor before I unhooked it.

Name:  IMG_20140824_142211313.jpg
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Old 08-24-14, 12:35 PM
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The wiring to the cap looks good.

This little clamp meter is $25 and it checks caps to 100 microfarad, volts AC and DC, Amps AC, flame rectification, temperature, and ohms. I don't own it but I probably will pick one up for a backup.

http://www.amazon.com/dp/B00E3XA0IM/...I1EAZJ5R8AQZSZ
 

Last edited by Houston204; 08-24-14 at 01:08 PM.
 

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