External AC Unit: Fan Turns Off & Noise Increases (with Video)

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Old 05-20-15, 07:23 PM
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External AC Unit: Fan Turns Off & Noise Increases (with Video)

Hi Folks,

I have to fix this old system a couple times a year, but I haven't run into this problem before: The external AC unit behaves fine* for several minutes, but then the fan shuts off and a buzzing noise gets increasingly loud.

https://www.youtube.com/watch?v=W8UVYJwf8Qc

What's going on here?

Thanks,
Jamie

*
  • Outdoor temp: 85
  • Condensor coil temp: 120
  • Temp at intake: 80
  • Temp at register: 71
 
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Old 05-20-15, 09:20 PM
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That buzz is the sound of your compressor running under extremely high pressure due to no cooling from the fan. This must not be allowed to continue or permanent compressor damage will occur.

You could have a defective fan motor or capacitor. You could check the fan motor after it stops and see if it's red hot. My guess is it will be and will need to be replaced.

There could be an outside chance that you have a bad capacitor.
If we're talking about an older unit.... I'd replace the fan motor with a new one and it's recommended capacitor.
 
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Old 05-23-15, 07:49 AM
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Hot Fan Motor

I've had the fuse pulled since I discovered the problem.

I did some testing yesterday. The outside air temp was 70, and the external unit ran for a whole cycle without the fan stopping. During that cycle, the fan motor housing ran 145.

The next cycle, it ran at 145, then went up to 160, and then the fan slowed to a stop. After stopping, the motor housing quickly went up to 180 (and then I pulled the fuse again).

I guess this is the kind of heat you were alluding to.

I'm reading about how the wrong capacitor can cause problems, too. I replaced the dual cap last year or the year before. I know I would have gotten a matched part, but now that I want to verify, I can't seem to find a parts list for this model.

Also, to save some cash, can I just test the capacitor with my tester?

Thanks,
Jamie

Notes to self:
  • Fedders model: C1030BBD1V Rev: W1
  • Current cap: 45+5MFD 5% 370VAC 60/50Hz
 
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Old 05-23-15, 09:06 AM
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Unknown Motor

FWIW, the capacitor (rated at 45/5 μF) tests at 44.6 and 5.1 μF, respectively.

There's no longer any print left on the motor's label, no parts list came with the unit, and I can't find anything for it on the internet.

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I'm not sure where to go from here, and I'm open to suggestions.
 
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Old 05-23-15, 09:12 AM
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You can buy a meter that check capacitors. Using a regular VOM is inconclusive. Normally I carry different size caps with me and just sub them in. I carry a capacitor checker but very rarely use it on A/Cs.

I cannot find the particulars on your Fedders C10 unit.

I would say if that cap ran an entire year then you most likely put in the right part last year.
As to now.... I gave you my recommendation already.
 
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Old 05-23-15, 09:24 AM
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Maybe this Motor

Well, my unit is a C1030BBD1V Rev: W1, but...

This site lists a C1030BD1VF-1, which has a (no longer stocked) motor, but lists the old part number as crc3590a0.

The latter part number is available on Amazon, and the specs seem to match up with what I'd expect--5 μF cap requirement and 1075 RPM (mine runs at 900 RPM with the fan attached).

I'm going to the parts store to see if they've got one; otherwise, I might pull the trigger on that one on Amazon.
 
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Old 05-23-15, 09:31 AM
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The specs I found for your unit. That Fasco unit on amazon looks close.

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Old 05-23-15, 12:54 PM
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Bought

My local guys didn't have the part, but I grabbed that one off of Amazon, and it will be here 5/28. (I may have to shorten the shaft, but we'll see.)

I'll post an update with the results.
 
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Old 05-23-15, 01:04 PM
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I would agree with shortening the shaft.
 
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