AC Unit only engages when manually pressing contactor button

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Old 05-07-18, 06:59 PM
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AC Unit only engages when manually pressing contactor button

Hello. Like the title says, I'm having problems with my ac unit. I believe it is a tempstar nac060aka1. The other day I first noticed the problem. The indoor fan was blowing but the AC unit would not turn on. Reading various post I thought the capacitor might be the problem .I pulled it out and did a voltage check. The label reads 60 + 5 however I was only getting 55 + 5. So I went about replacing the capacitor. I decided to also replace the contactor. Everything is in place but I'm still getting the same results. When II manually push the contactor button the unit comes to life .

i have checked voltage coming to the contactor. I read 240 at the bottom and 0 at the top .individually, the wires on either side of the contactor read 27 volts . However when I try to pull a reading from one side to the other I get no volts.

I'm stumped.
 
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Old 05-07-18, 07:28 PM
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Don’t read to ground.
Your unit isn’t getting a call to run.
Don’t press the contactor down. Besides possibly harming the unit it’s not safe for you. Look up electrical arc flash.
 
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Old 05-07-18, 08:14 PM
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Welcome to the forums.

Check for 24vac where the thermostat cable comes out of the house and attaches to the wire leads of the condenser. Check directly across those two wires. If you have 24vac there..... you most likely are low on refrigerant and the low pressure switch is opening the circuit keeping the 24vac from the contactor.
 
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Old 05-07-18, 08:33 PM
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Thanks for the quick reply PJ. When I go across the connector, yellow to yellow, I get 0 volts .
 
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Old 05-07-18, 08:41 PM
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Maybe I misunderstood. Do you mean to test the two wires coming from the furnace? One is red. Individually, it measures 20.27 volt .The other is white. It measures 27.29 volts. Do you want me to expose the leads to the white and red and see what reading I get if I connect red and white with my multimeter and see if 24 vac is the result?
 
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Old 05-07-18, 08:44 PM
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If my previous response is on point, do I set the thermostat to cool before testing or should it be off?
 
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Old 05-08-18, 03:40 AM
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Make sure the thermostat is calling for cooling. Test the contactor coil. Then thermostat conductors at the outdoor unit connection.
DO NOT test to ground. Test between the conductors on the control circuit.
 
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Old 05-08-18, 04:14 PM
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Yes.... you need to be in cooling mode.

You've already told us that you did not get 24vac across the two contactor coil wires.
I've asked you to check the wires coming from the house. Yes.... the red and white wire.
Check ACROSS the red and white wire..... not to ground.
 
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Old 05-09-18, 03:10 PM
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After further troubleshooting, I was able to narrow it down to the control board. Replaced the board and all is working as it should. Thank you for the input and guidance. It helped me to better troubleshoot the situation.
 
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Old 05-09-18, 04:08 PM
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Good job. Thanks for letting us know the outcome.
 
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