A/C Problems? Contactor, Board, Or Capacitor? - HVAC - DIY Chatroom Home Improvement Forum

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Old 05-09-2011, 03:13 PM   #1
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A/C problems? Contactor, Board, or Capacitor?

Installed a new capacitor last week and the air would come on sparringly. The capacitor is different from the one that was bad, a plastic grey one with a lip that fits into the hole of the rheem unit. The new one is a protech 55/5-mf 370v. The new capacitor reads 55 mf and 4.7 mf when checked. I'm getting 242 volts to contactor when testing L1 and L3 and when I engage the starter bar T1 and T3 reads 242 volts, turning the fan and compressor on. I cleaned the contactor with contactor spray. What am I overlooking?


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Old 05-09-2011, 03:27 PM   #2
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Your high voltage is good to the unit. What are you reading for voltage to the coil part of the contactor when you are calling for cooling? Check the 2 small thermostat wires that come into the A/C unit and tie onto the bottom part of the contactor. They should have 24 volts on them to make the contactor pull closed when calling for A/C. If you have 24 volts on them and the contactor doesn't close then the contactor is bad. If you don't have 24 volts there then you have to see where you lose the 24 volt signal from the stat in the house. maybe those wires broke outside, maybe the stat is no good, maybe a bad connection in the furnace. Just a few suggestions.


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capacitor , contator , control board

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