A/C compressor not turning on

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Old 09-03-16, 12:52 PM
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A/C compressor not turning on

The control transformer went out in my indoor unit. After replacing it, everything seemed to be working but air was not blowing cold. I went to the outdoor unit and discovered the compressor was not kicking on. The contactor is working fine but the capacitor was not reading the full capacitance so I replaced it. Still nothing. I checked resistance between all legs of the compressor and it looks good. The compressor is not open to ground just not kicking on. The one thing that seems fishy is that accros the fan capacitor there is 440 volts but only 280 across the compressor cap. Is this normal? What else can I try?
 
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Old 09-03-16, 01:05 PM
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Welcome to the forums.

You said the compressor is not starting up. That means the condensor fan is running normally ?

You can't measure voltage across caps like that.
 
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Old 09-03-16, 01:19 PM
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Yes the fan works fine. And by voltage accross the caps I mean with the unit running
 
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Old 09-03-16, 01:27 PM
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Ignore any voltage reading across a cap. The caps job is to change the AC's characteristics which will affect a meter.

Is the compressor real hot causing it to be dead on thermal overload ?

There are three terminals on the compressor. You should get three resistance readings. The lower two readings should equal the highest one.

Always wear safety glasses when working directly on a compressor.

IF the resistance readings are correct and IF you have 240vac to the compressor it must run.

At this time.... a make and model number would be helpful.
 
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Old 09-03-16, 01:33 PM
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I did get three resistance readings between each terminal of the comp. 1, 3 and 4 ohms. It is not hot and the make and model are Copeland CR32KF-PFV-130
 
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Old 09-03-16, 01:46 PM
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That is correct. Start 1 ohm plus run 3 ohms equals 4 ohms total.

You've confirmed 240v on the C and R terminal ?
If yes.... then it sounds like the compressor broke a rod internally. The internal motor is running but is not coupled to the compressor section.

You should be able to disable the fan. Push the contactor in manually and hear the motor run inside the compressor.
 
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Old 09-03-16, 02:06 PM
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It hums for a few seconds and then it is silent. It sounds more as if the motor is trying to turn but can't
 
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Old 09-03-16, 02:10 PM
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It sounds like you have a starting issue. You changed "a" cap. Did you change the right one ?
 
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Old 09-03-16, 02:34 PM
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There was a single dual capacitor it measure 5 uf on the fan side and negligible on the herm side (supposed to be 35) I could not find a similar dual cap so I left the existing one tied to the fan and put in a single 35 uf with the same voltage rating tied to the comp
 
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Old 09-03-16, 03:16 PM
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It sounds like it's not wired correctly. A picture or two would help us. http://www.doityourself.com/forum/el...-pictures.html
 
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Old 09-03-16, 03:52 PM
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The only wiring i changed was to move the blue wire from the comp to the new cap and add the white wire from the new cap to the common on the contactor
 
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Old 09-03-16, 04:27 PM
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White should connect to Run not Common.

What is the make and model of this condenser?
 
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Old 09-03-16, 05:27 PM
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The white is connected to the same terminal as the red wire on the fan capacitor which is working fine. the label on the condensor is pretty faded but I believe it is an International Comfort Products model NO. NAC036GKA
 
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Old 09-03-16, 06:21 PM
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It looks like the compressor red and black wires are crossed on the contactor.


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Do you have a readable diagram inside of the service panel?

http://www.gotempstar.com/go/index.asp?t=
 

Last edited by Houston204; 09-03-16 at 07:17 PM.
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Old 09-03-16, 07:29 PM
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Wow...... I feel like an idiot. The black and red wires were swapped on the contactor..... I had taken the contactor off to check before I checked the cap and I must have swapped them when I put it back..... compressor started right up and it's blowing cold air!!!!!! Thankyou so much for help and i'm sure my family will be thankful too now that our house will drop below 90!!!
 
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Old 09-03-16, 08:10 PM
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That is great news.

The Com label on a dual capacitor is misleading. It is common to Herm and Fan but it is the Run circuit.
 

Last edited by Houston204; 09-03-16 at 10:48 PM.
 

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