Condenser stopped working


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Old 07-12-20, 07:13 PM
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Condenser stopped working

Hi, my central AC suddenly stopped working yesterday. I tried to troubleshoot the problem and found that both the fan and the compressor in the condenser were not on. I measure the capacitances of the dual-run capacitor in the condenser and they are within the normal range. I also found that the low voltage (25 VAC) from my thermostat reached the contactor and the contactor was working properly. I also tested the continuity from the line side to the load side of the contactor using my multimeter and the continuity was established when the contactor pulled in. However, there was no voltage across the line side of the poles or the load side of the poles. But if I measure from any pole to ground, I got 120 VAC.


I then measured the voltage coming out from the AC disconnect when the AC disconnect was on. I found that any line or load pole to the ground is 120 VAC. However, there is no voltage between the line poles (between Line 1 and Line 2 in the picture shown below) or between the load poles. From all the information I could find, it seems the voltage between the line poles and between the load poles should be 240 VAC for the condenser to work. I also measured the voltage between the poles of panel breaker in the basement for this condenser. It showed 240 VAC. By the way, no breaker was tripped at all when my AC suddenly stopped working. Resetting the breaker didn't fix the problem.




At this point, I am not sure where the problem is. Perhaps the AC disconnect is faulty and/or the wires between the panel breaker and the AC disconnect are damaged. Or perhaps the voltages between Line 1 and Line 2 are in phase so that I measured 0 VAC. Please let me know what you think. Thanks in advance!
 
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Old 07-12-20, 08:15 PM
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Welcome to the forums.

Is this outside ?
If it is...... there should not be NM-b type cable connected to it.
NM-b cable aka Romex is for indoor use only.

Plain and simple...... there needs to be 240v across the white and black wire.
When the "pull out" is in..... there should be 240v across the red and black.
 
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Old 07-12-20, 08:34 PM
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Hi Pjmax,

Thanks for your quick reply! This is a outside AC disconnect and I removed a protective housing before measuring the voltages. The previous owner of the house installed the AC disconnect and I have no idea why he (or someone he hired) installed the NM-b Cables.

I agree with you that it should be 240 VAC across the white (Line 1) and black wire (Line 2) and 240 VAC across the red (Load 1) and black (Load 2) when the "pull out" is in. However, every wire is measured 120 VAC to ground, but 0 VAC across the lines, and 0 VAC across the loads.
 
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Old 07-12-20, 08:38 PM
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Then you have lost one of the legs of power. It would be extremely rare for the wire to have gone bad but if you measure 240v at the breaker..... there is a break or a splice box in between.
 
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