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mecdatlanta · 10-17-2018, 11:56 AM

Hey All,

One of my AC units needs a new fan capacitor. It makes a humming noise, but the fan will start if given a little spin.

Unfortunately, the diagram, which was made of paper, has lost almost all of its ink. Can anyone tell me which of the two capacitators is for the fan (the bigger one on the left, or the smaller one on the right)?

Deep Water D · 10-17-2018, 12:07 PM

How do you know it's the capacitor if you don't even know which one goes to the fan? A bad fan motor bearing will cause the exact symptom you describe. Grab the fan motor shaft and see how much up and down slop there is. Shouldn't be much if any.

mecdatlanta · 10-17-2018, 12:49 PM

Quote:

Originally Posted by Deep Water D

How do you know it's the capacitor if you don't even know which one goes to the fan? A bad fan motor bearing will cause the exact symptom you describe. Grab the fan motor shaft and see how much up and down slop there is. Shouldn't be much if any.

There is no play in the shaft. The fan capacitor is my best guess at this point. I just don't know which one is for the fan vs. compressor.

**Lt Dan** · 10-17-2018, 01:02 PM

Quote:

Originally Posted by mecdatlanta

There is no play in the shaft. The fan capacitor is my best guess at this point. I just don't know which one is for the fan vs. compressor.

Look for the uF (microfarad) numbers on the capacitors. The one with the smallest number will be for the fan due to the lower amperage draw. It will probably be somewhere in the neighborhood of 7.5uF.

Here's a good video on how to test capacitors to see if they are good. This is done on a double capacitor, but the principle is the same.

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

mecdatlanta · 10-17-2018, 06:39 PM

Quote:

Originally Posted by Lt Dan

Look for the uF (microfarad) numbers on the capacitors. The one with the smallest number will be for the fan due to the lower amperage draw. It will probably be somewhere in the neighborhood of 7.5uF.

Here's a good video on how to test capacitors to see if they are good. This is done on a double capacitor, but the principle is the same.

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

Thanks Lt Dan. I tested the two capacitors and this one was not accepting a charge. The problem is, I can't find a replacement. I tried typing in all of the codes I could find on the unit (Googling and looking on Amazon). Any ideas?

KanzKran · 10-17-2018, 06:50 PM

https://www.amazon.com/Motor-Dual-Ca.../dp/B00C0YSSZS

No picture, though.

ron930cab · 10-17-2018, 06:57 PM

OP, just changed mine. May depend on your AC model/brand. On my Dometic Penguin 15K, the larger is the run cap (50/15 uf) and the smaller black one is the start cap (47-56 uf). You could just replace the run cap that starts the fan too. But I would replace both. Got them from GetRVParts.com. But you can get elsewhere too including Amazon.

ron930cab · 10-17-2018, 07:07 PM

One more thing, you may want to Google the model of your AC for a parts list to verify the Cap sizing. Mine were the wrong uf from a previous repair. If you have a second or third AC, check to see what they have for sizing.

mecdatlanta · 10-17-2018, 07:16 PM

Quote:

Originally Posted by ron930cab

OP, just changed mine. May depend on your AC model/brand. On my Dometic Penguin 15K, the larger is the run cap (50/15 uf) and the smaller black one is the start cap (47-56 uf). You could just replace the run cap that starts the fan too. But I would replace both. Got them from GetRVParts.com. But you can get elsewhere too including Amazon.

Thanks Ron930cab. But when I google "run cap (50/15 uf)", I see images of capacitors that have only two connectors. Mine has three (as seen in the pic). Am I missing something?

mecdatlanta · 10-17-2018, 07:24 PM

Quote:

Originally Posted by KanzKran

https://www.amazon.com/Motor-Dual-Ca.../dp/B00C0YSSZS

No picture, though.

Does it have 3 terminals? I seem to only come up with capacitors that have 2 terminals every time I google for it.

ron930cab · 10-17-2018, 07:26 PM

mecdatlanta, it has three sets of terminals (each with multiple terms) like the one you show in the pic. But your size may be different. I just googled run cap 50/15 and got a Dyers RV with a picture a second ago. For my coach the middle air had never been serviced, so those caps were OEM. I used those sizes and then googled until I got the same info from another source (like Dometic Heat Pump 15K...).

KanzKran · 10-17-2018, 07:29 PM

It's a 10 + 20 µF dual-value capacitor. Has three terminals: "F" for fan, "H" for the compressor (hermetic), and a common.

chuckftboy · 10-17-2018, 07:35 PM

The larger cap with a metal body is a duel capacitor. It has 1 common terminal and one for the compressor, the third terminal is for the fan. Start capacitors are made of Bakelite (type of plastic).
Ron930 had it correct and the microfarads (Uf) is printed on all capacitors of that size. Any air conditioning supply, or appliance store can match one up for you.

mecdatlanta · 10-17-2018, 08:17 PM

Quote:

Originally Posted by chuckftboy

The larger cap with a metal body is a duel capacitor. It has 1 common terminal and one for the compressor, the third terminal is for the fan. Start capacitors are made of Bakelite (type of plastic).
Ron930 had it correct and the microfarads (Uf) is printed on all capacitors of that size. Any air conditioning supply, or appliance store can match one up for you.

That might be the easiest thing to do. I;m amazed at how ambiguous this whole process is. Amazon definitely doesn't have this down. Not sure that any online sites does.