A/C Unit compressor noise


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Old 05-14-10, 01:36 PM
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A/C Unit compressor noise

I decided to take a stab at learning something new and save some money at the same time by attempting to fix my A/C unit all by myself (feel like a youtube video of my AC unit taking off into orbit is just on the horizon). The A/C unit fan quit working and all I heard was a loud humming noise. So I disconnected the power to it then I assumed at the time this was the Fan Motor. So I took the panel off the side and found some wires going from the house to a switch, then from that to a capacitor the size of a beer can. The capacitor was most obviously kaput seeing as how the one end of the cylinder was completely swollen out. The capacitor was a three prong/terminal capacitor. It had 3 labels, a Brown Wire coming from the fan motor hooking up to the "fan" hookup, then a "C" that was hooked up to yellow insulated wires and a "hern" that was filled with blue insulated wires". Anyways, it's hot outside, so rather than look up the best price online for the parts I disconnected the motor from the fan and ran off to some parts dealer place on the opposite side of town and asked fora suitable motor the replace the apparently dead one in hand. The guy at the store ran off to the back and grabbed a new motor, it was about the same size but was obviously a different make and model with a much longer fan shaft and it came with a new capacitor. The old motor had 3 wires, a Yellow, Black, and Brown, where Brown was the Fan. this new motor had more wires. He assured me the white one was the same as the yellow and the black went to black and brown to brown, but there was also the green (ground wire), and this mysterious brown/white wire. He hooked up the Brown to one side of the capacitor ( a new 2 prong/terminal capacitor) and the brown/white one to the other side, so I took it home and hooked up the White (same as yellow) to the brown side of the capacitor, and the blue ones going from the compressor to the brown/white side. There was also another set of blue/wires coming from what I'm guessing was a solenoid to each side of the capacitor (blue with blue and yellow with yellow). Hooked it all up and turned the power on and it worked miraculously enough. However, the A/C unit does make this compressor-like straining turning on sound periodically so I've kept the power off in case I may have something hooked up improperly. Maybe the Fan isn't attached securely enough? I did cut off about half of the Fan shaft with a hack saw to allow enough clearance between it and the insulated wrap around the tank in the bottom.

Anyways I feel like the blue compressor wires going to the capacitor are hooked up improperly or maybe the 2 prong capacitor isn't the right kind for what I need and I need to replace that with a 3 prong. I can take a photo or draw up a schematic. I know without something visual like that I cant follow along either.

PS: motors for these things are way too expensive for what they are. I paid 127 dollars for mine, found it online for about 100 + 10-15 s/h. The first place I went to wanted 283 dollars for the motor, mein gott.

On the plus side the fan does rotate in the proper direction and the air is flowing in the proper direction. The new motor is a Fasco D793 (825 rpm, 1.0 amp, 1/6 HP) with half the fan shaft hacked off, probably voided the warranty with that). I'm beginning to even wonder if the motor was the faulty part, maybe it was just the capacitor, hrmm, maybe I should order a new 3 prong cap on Monday and hook up the old motor and see what sparks fly.

Any advice or input?

-Thanks in Advance
 
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Old 05-14-10, 05:46 PM
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follow up schematic

 
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Old 05-14-10, 06:36 PM
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what ur saying is very jumbled and hard to read so im going to tell you how i hook up new fan motors. first thing i do is tear off the green wire on the bottom of the motor. my motors have 4 wires, 2 brown wires and a black and a white. the two brown wires hook up to the new mini cap. and the black and white both hook up to the contactor, preferrably one of the left and one on the right. make sure its the unpowered side when the contactor is not pushed in. and the old 3 prong cap should remain in the unit, untouched.
 
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Old 05-14-10, 06:54 PM
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well, maybe i should re-write my original post then, hrmm. the new motor works fine and is hooked up properly, the old capacitor is dead, hooking anything up to that swollen canister is a bit pointless. the problem now appears to be the compressor as it makes a very loud noise when it tries to start up roughly every 20 or so seconds. where i'm at now is either the new capacitor isn't compatible with the old compressor or something is actually wrong with the compressor. I'm hoping its the former since they're cheaper. I'm fairly certain I hooked up everything properly. Is it possible if the new motor requires more electricity than the old one then the old compressor isn't getting enough electricity or would it just draw what it needs regardless. maybe I should try bypassing the capacitor temporarily and just see what happens..though that might be a bit dangerous..
 
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Old 05-14-10, 08:19 PM
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why...........

Originally Posted by ender2272
what ur saying is very jumbled and hard to read so im going to tell you how i hook up new fan motors. first thing i do is tear off the green wire on the bottom of the motor. my motors have 4 wires, 2 brown wires and a black and a white. the two brown wires hook up to the new mini cap. and the black and white both hook up to the contactor, preferrably one of the left and one on the right. make sure its the unpowered side when the contactor is not pushed in. and the old 3 prong cap should remain in the unit, untouched.
........are you saying to "rip off" the green wire off of the motor????in case of a short the whole top of the unit can just be waiting for someone with wet feet to touch the unit & get ?????????imho.........Jack
 
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Old 05-15-10, 02:01 AM
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i've been reading up on some websites and i'm pretty sure its the capacitor and compressor issue. I'm going to hit up some dealer on monday with the old cap and get another exactly like it, unhook the new motor and put the old motor back on it
and see what happens. Ripping the green/white ground wire off isn't necessarily the best idea, but if the AC unit itself is already grounded then the additional grounding shouldn't be necessary (unless something happens to where it no longer is grounded), but sometimes its just nice and safe to have a little redundancy.[and by something i mean some cute and cuddly furry little rodent]
 
 

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