Outdoor unit fan and compressor wont start

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  #1  
Old 07-17-10, 10:14 AM
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Outdoor unit fan and compressor wont start

I have a Frigidaire 2-ton (Model FS3BA-024KA) split AC Unit.
The fan and compressor in the outdoor unit wont come on.
I watch the outdoor unit as my wife turns the thermostat to cool. There is a black plunger switch that pops in with a very noticeable click. But the fan doesn’t come on and I cant hear any sound from the compressor.

There doesn’t seem to be many parts out here. There is a large capacitor and it is connected to that switch that moves when the thermostat is set to cool. The capacitor is also connected to a small circuit board. Even though the switch pops in, the fan doesn’t come on at all. I watched for 15 minutes.
Is the problem more likely that little circuit board, the capacitor, or the black plunger switch? (Or something else)
Is there some test I can do or voltage I can check to isolate the problem?
Thanks in advance for any suggestions.
 
  #2  
Old 07-17-10, 11:53 AM
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Check that the circuit breaker isn't tripped.

If you have a voltmeter, and know how to use it safely: with the thermostat calling for cooling, see if you have 240V on the line and the load sides of the condenser contactor. If you have 240V on the line side but not on the load side, replace the contactor.
 
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Old 07-17-10, 07:18 PM
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When the contactor activates is that from the 24v line that comes from the thermostat? The circuit breaker is not tripped. When I manually turn the circuit breaker off out in the garage for the AC unit, the thermostat in the house goes blank as if it gets its power from there also. Thanks for the suggestion - I had thought the voltages were good outside because I heard and saw the contactor switch activate. But now I realize that is controled seperately and is used to close the circuit for the 240v.
 
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Old 07-18-10, 08:05 AM
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Did you check the 240V at the load and line sides of the contactor?

Yes, the contactor coil operates at 24V.
 
  #5  
Old 07-18-10, 08:21 PM
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I fixed it !

Thanks Mike! This suggestion got me on the right track to my resolution.
I took a multimeter and saw the 240v at the entry to the contactor switch. When the thermostat was put to cool I could see the contactor activate but yet the 240v was still not present at the exit terminals of the contactor switch. I disconnected the wires from the contactor exit side and still no 240v at the exit. So I took the contactor switch off so that I could take it with me to a parts store to get a new one. But while looking at it in the house I discovered that it comes apart quite easily. I took it apart and found that the place where it makes contact was quite dirty and looked somewhat corroded. I then cleaned the contacts with an emory board and re-installed the contactor switch... HOUSE COOL AGAIN; YEA !
 
 

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