AC Compressor Start Up Issue (High Current Draw)

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Old 08-19-15, 06:39 PM
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AC Compressor Start Up Issue (High Current Draw)

I happened to be outside last night when the AC compressor for our first floor AC system tried to start up. The house lights dimmed appreciably and the compressor did not start. A few minutes later the same thing happened but this time the compressor started. (Iím guessing some kind of thermal overload protector reset itself). The system has worked fine since then (many on/off cycles).

Today I checked a few things on the outside compressor unit. I was able to remove a plastic cover from the contactor. The contacts look pristineóno indication of overheating, discoloration, arcing etc. None of the wires show any indication of overheating. The dual 50/5 uF capacitor shows no evidence of bulging or fluid leakage. My multimeter seems to be on the fritz so I canít test the cap. (It canít read capacitance values anyway). Until I get hold of a suitable meter I have a few questions.

Do bad capacitors always show bulging or fluid leakage? Or can they fail and look just fine? The compressor seems to be getting the signal to turn on so I think that knocks out things like the thermostat, 24V transformer, low voltage wiring, etc. What else could be causing a very intermittent hard start problem?

This unit is a Goodman CRT361A. Itís about 8 years old, as is the house. The main electrical panel is rated at 200 amps. The circuits that power each compressor are rated at 40 amps each.
 
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Old 08-19-15, 06:50 PM
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I would recommend replacing the capacitor first.

How far is that condensor from the panel ?
 
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Old 08-19-15, 07:16 PM
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Not that far away. They're both on the same end of the house. I'd estimate the cable length from the panel to the outdoor box is not more than 25 feet.
 
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Old 08-20-15, 06:43 AM
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I'm pretty sure this capacitor is a run capacitor. How would a bad run capacitor affect the motor start-up?
 
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Old 08-20-15, 07:05 AM
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Some caps can look good and still be bad or weak. The cap for the compressor is wired to the start winding's. I just call them start cap's. Is that is technically correct, I don't know.
 
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Old 08-20-15, 07:07 AM
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Capp first then a SPP6 if still doing it.
 
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