Ac problems/ not cooling down


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Old 07-07-14, 08:18 AM
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Ac problems/ not cooling down

hello, we just moved in to our house about 2 months ago. the air was working great when we first started it. we have an air conditioner for each floor. the top floor is great , the bottom is the problem. last week the air wouldnt come down in temp. the fan is not spinning on the unit itself outside. i took the cover off and restarted the unit and it started working again. however the house still wont come down. the fan has stopped again. the house is only 6 years old. does it sound like it needs freon? i was told that if it needs a recharge that that is why the fan stops working? the pipe going in to the unit is not cold, like the other unit that is working. also there is no freezing on the pipes in the house, no condensation either. any ideas?
 
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Old 07-07-14, 08:29 AM
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Low freon wouldn't effect the fan. When the fan stops working, the compressor will eventually overheat and shut down. Replace the capacitor first and see if that works.
 
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Old 07-07-14, 09:49 AM
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wouldnt the capacitors top be like "popped" if it was broken. i was reading up on it and most sites say the top would be bulging.
 
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Old 07-07-14, 09:52 AM
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While you're correct that a bulging top is indicative of a bad capacitor, they can go bad and not show any visible signs (bulging). Since capacitors are relatively cheap, go ahead and replace it.
 
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Old 07-07-14, 12:06 PM
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i am going to try to replace it. also, i dont hear any humming noise coming from the unit when the fan isnt going, is that a good or bad thing? the air coming in from my vents is cold, but i know that i need to shut the air off because i dont need to blow the whole system. does anyone think that it could be the fan motor?
 
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Old 07-07-14, 12:33 PM
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And bulging can be quite relative. If you could compare 2 identical caps, one slightly bulged and one not, it's very easy to tell. When you do it every day in your job, it's also easy to tell. When you've never seen a slightly bulged cap like that (or once every 10 yrs), it's not so easy to see.

I worked electronics for 24 yrs, and saw all sorts of good and bad components big and small. 5 yrs after I retired, my A/C quit and I seriously couldn't tell if the cap was bulged or not. It didn't look it to me, it looked almost new, because I kept my unit very clean (always good to have a clean unit...lol). Took it to a supply store and he measured it and showed me what a new one should look like. Then I could see the slight crown to the top.

Anyway, as said, they can still be bad with no external sign.

No humming means the comp isn't starting either, also a sign of a bad cap.

You are correct that with low charge, the fan won't start or run either. There is a pressure switch that will open the control voltage to the contactor that applies high voltage to the fan and compressor.
 
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Old 07-07-14, 12:39 PM
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Oh, and it may not be the cap...you could have another issue, but it's a cheap and simple part to replace.
 
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Old 07-07-14, 02:48 PM
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i listened closely and i can hear a humming. i pushed the restart button again and the fan went when i pushed it with a long stick. however after a half hour it went off again. there is this dark gray thick gooey stuff that is on the bottom of the capacitor. im hoping that if i replace that that it will start working. what else, that is a cheap fix do you think it could be?
 
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Old 07-07-14, 03:05 PM
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Gooey stuff almost always means a cap has split and leaked the oil(?) inside. I'm not sure of the restart button you mention unless its the top of the contactor?

Replace the cap with the correct one (take pics and label the wires, turn off power first and Google for discharging a cap) and if still no joy, we could move from there.

$50 bucks in parts (cap) and tools (multimeter) could save you hundreds.
 
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Old 07-08-14, 10:24 AM
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so just wondering, i am having my husbands uncle come out thurs to look at the unit and i was gonna buy the capacitor first, is there certain sizes? also is there anything else that i should buy that he will need to replace it. i have had my air shut off since yest afternoon and i just turned it on and cold air is definitely coming out of all the vents. but the fan outside is not spinning.
 
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Old 07-08-14, 10:54 AM
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Cold air will come out until the compressor overheats and shuts down. Not good to run it that way, can damage compressor and then yer talking real money.

Yes, there are different sizes. You'll need to cut the power at the breaker or disconnect, remove the top or access panel where the cap is located. The cap is an oval or cylindrical black or silver "can" about the size of a small soup or tomato juice can. Carefully make a drawing of where the wires go (pictures are good as well), then remove the cap to get the specs on the side. Do a search for discharging and removing a capacitor. You can get a good shock if it still has a charge on it. Sometimes they can be hard to read in which case you need to look at the fan motor and compressor spec plates to see what is required.

Normally a cap will have something like 30/5 MFD 370/440 VAC It may only have a single number in the first group if you have separate capacitors for compressor and fan, which you may. The second group of numbers is the voltage rating, higher is ok but never lower. If yours says 370...you can use a 370 or 440.
 
 

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