compressor not coming on


  #1  
Old 07-03-09, 09:33 PM
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compressor not coming on

I think that is whats happening anyway. It was working earlier today then this evening it stopped cooling. The fan blows though inside and on the outside unit also.

Here's some history that will probably provide a clue as to what might be wrong.

When the unit was originally installed (new) the tech did not have a pull out box for the compressor and used a box with two "one-shot" fuses in it... in other words if they blow you throw them away. The holder that clamped the ends of the fuses was loose from the factory (I figured this out later) and I believe it was causing some voltage drop across the connections for each fuse. Eventually, after a couple of years one of the fuses blew. It was replaced and I noticed the problem with the fuse holder so I later replaced it with a regular pull-out box myself. I am thinking at this point that the compressor was running on low voltage and the extra current blew the fuse and probably did some damage (weakened) to the motor... this worked for about a year then last summer the big capacitor (run cap?) went bad, tech replaced it. Yesterday the same cap went bad again (leaked oil) and the compressor kept kicking the 40amp fuse inside the house every time it tried to come on. I replaced the cap myself. The unit ran and cooled fine for ~36 hours then started kicking out the fuse again. It did this about 3 times, I reset it and it would seem to go ahead and run and cool ok. Then a couple hours later (this evening) it just stopped cooling... and its not kicking out the fuse any more so I think the compressor isn't coming on at all. As I said above the fan on the outside unit runs. I just think the compressor motor isn't.

I have no idea what to try next. I'm afraid the compressor motor is shot. The unit is 7 years old. Anyone got any ideas?

Thanks
David
 
  #2  
Old 07-04-09, 11:04 AM
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Did the new cap match the old one? [uf and vac ratings] Is the compressor hot or cold to the touch?
 
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Old 07-05-09, 06:14 PM
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Thanks for the reply. yes the cap was a 55/5uF rated at 440v and matched the old one. I haven't tried to feel the compressor. I suppose I could do that, how should I go about it? It's got a grill, fan and then a shaped blanket (of sorts) covering it.

Guess I could take everything partially loose, then run it, then quickly disassemble the top part so I could get my hand down on it before it has time to cool off... I'll let you know. thanks.
David
 
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Old 07-05-09, 06:34 PM
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I just tried running it again since my first post the other day. It tried to come on, the breaker box made a humming noise for about 1 second then just popped the breaker. I reset the breaker - same thing again. It just won't run now.
 
  #5  
Old 07-05-09, 08:47 PM
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If you have a test meter, isolate the terminals on the compressor [take the wires off the terminals so you just have the pins sticking out, make a sketch or take some photos of where the wires go]. Scratch a clean place on the larger tube that goes to the compressor then ohms test each pin to the clean spot on the tube. You should not get a reading. I foyu do, the compressor motor is grounded. Do the same with the fan motor, sketch, isolate the wires only this time you won't have pins, just the ends of the wires. Scratch a clean place [down to bare metal] on the body of the motor and test each wire to the body. Do the same with the cpacitor; it might be grounded but that's a streatch. Let us know what you find.
 
 

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