A/C condensor fan can not make up it's mind

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Old 11-04-17, 01:40 PM
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A/C condensor fan can not make up it's mind

First post. Thanks for allowing me to join... Two months ago, my AC fan stopped working so I replaced the capacitors and put in a brand new fan motor. What I did...


- Replaced both capacitors ( put in a three pronged one C- Herm -Fan... and a separate two pronged one for the fan. Left the Fan terminal empty on the big one and ran the fan to the separate small capacitor per advice from a friend who works commercial HVAC.)
- New fan motor


It has been running perfect until early this week when the fan stopped coming on.
I turned the unit on, spun the fan with a screwdriver, and it took off and worked. So i figured it was the fan start capacitor.
I rewired the fan wires to the empty fan terminal on the big capacitor, but it was the same result...
so i rewired the fan wires back to the separate fan capacitor.
After that, it wouldnt spin at all with the unit on. I tried starting it with the screw driver again, but it would not catch. I could hear the compressor running....
So i tried again an hour later and it only caught at maybe half speed, so i turned it off...
I tried again a few minutes later, and it caught at full speed, but only ran about 2 minutes before it slowed way down and stopped. I tried to restart it, but it felt seized up and i couldnt spin it.
I tried again an hour later, and it caught full speed and ran great for a couple hours until I turned it off because we were leaving and i didnt want it to catch fire or something....

Not sure what to make of it. I feel it would be unlikely for both brand new capacitors to not be functioning properly.. The fan motor is also brand new.. The unit itself is around 10 years old and has ran great for at least the past 4 years per the previous home owner.. Let me know what you guys think and I sincerely appreciate your time. Thanks in advance - James
 
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Old 11-04-17, 02:23 PM
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Are the caps an exact match (microfarad) ?
 
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Old 11-04-17, 03:27 PM
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As Skaggsje mentioned, are the fan capacitors the correct capacitance value for the new motor? The new motor may take a different capacitance value than did the original motor.
 
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Old 11-04-17, 03:33 PM
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Welcome to the forums.

If the motor is frozen now..... the windings are probably burned.
Feel if the motor is hot.

Was this a direct replacement motor ?
Was the voltage correct.... 240v ?
 
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Old 11-04-17, 05:04 PM
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After it had appeared to lock up, I let it rest a while and tried it again, and it worked. I am not home to check on the specs, but my wife said that it has been running flawlessly all day.... When I first looked at the unit earlier this week, I noticed a good amount of rust and condensation liquid in the component storage box. A lot of rust on the fan cap terminals. I cleaned them with a wire brush and re installed them... Is it true that caps have to build up a charge after all electricity in them has been discharged? now that it is running fine, could the initial problem been from the rusty terminals, with the subsequent problems being from the caps having lost their stored power? Sorry i am unable to check on the specs until tomorrow afternoon
 
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Old 11-04-17, 05:16 PM
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Is it true that caps have to build up a charge after all electricity in them has been discharged?
No. The cap will build up full charge in 1/30the of a second. Faster then it takes to blink an eye.

Rusty terminals are always a problem in any in any electrical application.
 

Last edited by PJmax; 11-04-17 at 05:50 PM. Reason: typo
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Old 11-04-17, 05:40 PM
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Ok I see makes sense. Thank you
 
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Old 11-04-17, 07:29 PM
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Well wife said it randomly died again and now the outside unit isnt even making a sound. What numbers am I looking for on the fan and caps to make sure everything is the right part?
 
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Old 11-04-17, 11:54 PM
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Universal replacement motors ship with drain plugs. I have seen homeowners forget to make sure that the drain plug is on top of the motor and the bottom plug is not installed.

When replacing an outdoor motor I match the frame size, RPM, voltage, horsepower and Full Load Amperage.
The capacitor must match the requirement of the new motor.

If I took this call I would suspect the drain plug, run capacitor, or FLA rating to be the issue.
 
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Old 11-24-17, 07:42 PM
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Hopefully this will help others with a condenser fan problem.

I am a new member and I have NO experience with HVAC systems.

I just had a similar problem with my heat pump system today and I was luckily able to find and correct the problem. I figured I would post my findings here, so maybe it will help you, gnr.10393, or someone else out there.

Earlier today my wife looked at the thermostat and asked me if the AC unit working. It was on and appeared to be working, but the inside temp was a couple of degrees off of the set temp. I walked outside to check the unit and I heard the compressor kick on and off a couple of times, but the fan was not running. I turned the system off and used a thin metal rod to try and spin the fan blades, thinking that maybe the fan motor was seized up. The fan spun just fine when I nudged the blade, so I figured that that must not be the problem. I kicked the system back on and went out to check it again. As I was watching it, I heard the compressor kick on and the fan still did nothing. I blew on the blade and it started moving, then it picked up speed and actually started running, however it was spinning in the wrong direction.

At this point I decided to use Google to research the problem and see what I could find. I ran across several applicable posts on this site and others. After reading through many of them, I was convinced the it must be a bad run capacitor. I decided to go take a look at mine and confirm the model number, before I ordered a new one. After confirming the model number and not seeing anything that was obviously out of place, I decided to remove a couple more panels so that I could inspect the wires all along the run. Behind one of those panels I found a bundle of wires that were passing through a metal knockout hole. I noticed that there was half of a plastic bushing in the hole, however several of the wires were resting directly on the metal. When I went to adjust the bushing, the brown motor wire immediately fell apart. The metal had completely cut through the insulation and it had begun to short out the wire.

I installed a new rubber grommet in the metal panel, then cut back the wire a bit and put a new connector on it. I kicked the system back on and everything worked perfectly. The fan started spinning as soon as the compressor kick on and it was now moving in the correct direction. PROBLEM SOLVED!!!

While I do realize that most of the time these symptoms would be due to a faulty run capacitor, it may be worth checking the wiring first. If had just ordered a new run cap, as I was about to, then I would have needlessly ordered a part and it wouldn't have fixed my problem. Hope this info can be helpful to others out there.
 
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