Outside A/C unit not turning on

Old 06-01-19, 07:47 AM
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Outside A/C unit not turning on

Hi everyone, I just got back from my honeymoon yesterday and had a pretty bad surprise, my house was 103° inside and my outside A/C unit was doing absolutely nothing.

I first checked my thermostat and made sure it was working. I put new batteries in it and it seems to still be controlling the inside fans just fine. I then checked the breakers and none of them seemed to be flipped. Just in case though I went through and turned them all off and back on. I then went and checked my capacitor inside the A/C unit and it looked great, still shiny and so disformation from what I could see.

The things I have noted are that the A/C unit does nothing. I can try and spin the fan and it will spin fine but it does not help it start. I also tried to pull the disconnect when I was going to open the A/C unit. I found that the disconnect was just about impossible to pull out and I ended up on my butt when it did finally come out. The contact on the right side looked a little corroded or maybe even melted in one spot.

The outside unit is the intertherm brand (I'm not sure what year I haven't lived at this house very long).

Thank you for any help or advice that you can give. I ran out to Walmart last night and picked up two window A/C units to try to fight the heat but they won't work forever.
Old 06-01-19, 08:49 AM
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If you have a voltmeter, check for 240VAC at the contactor (be very careful as 240VAC is lethal). The contactor is a relay. It has 240VAC (input) on one end. The control voltage (24VAC is usually connected to the terminals near the center of the contactor. When the thermostat calls for cooling, it sends 24VAC to the contactor coil, which pulls down the contacts, sending the 240VAC to the compressor and condenser fan.

If you don't have a voltmeter, or just want to do a quick check, take an insulated object (wooden or plastic "stick" and push in on the contactor in the center. If the compressor & condenser fan come on, you know that you have 240VAC present, and the capacitors are okay. Only manually push in on the contactor for a few seconds, as you could damage the compressor if the unit is low on refrigerant and you run it for a long time.

If the outside unit turns on when you press in the contactor, with the thermostat calling for cooling, check for 24VAC at the wire nuts where the control cable (from the house) connects to the outside unit. If you have 24VAC present at the wire nuts, you may have a low pressure switch which is preventing the outside unit from turning on. If you don't have 24VAC present, an animal may have chewed through the cable coming from the house.

Let us know what you find.

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