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I have a Lenox system that is AC only (my heat is separate). On occasions, maybe 10-20% of time, it doesn't cool and the fat refrigerant pipe coming out of the air handler going to the condenser outside is warm, whereas it's cold when it does cool. I think there is no refrigerant flow between the inside unit and the compressor when it's not cooling, there is also no water draining out, I took the hose out of the pipe and put it in a bucket to test

I had a technician come over and he confirned the system is properly charged with refrigerant. When he was here was the other 80-90% of the time when it works so I wasn't able to reproduce the issue. It was $150 for his visit to basically tell me everything is fine. To reproduce the issue, I would have to have him stay here until it shows again.

I am trying to get some ideas of what MIGHT be the cause of this happening before I spend another couple hundred dollars to be tdld the same thing.

UPDATE: I have determined that, when this is occurring, the condenser (outdoor unit) fan is blowing but the compressor is not, therefore no cooling is taking place. As per some research, I decided to replace the capacitor as it was easy and cheap to do even if it doesn't do the fix. Since this issue is only intermittent, I do not know if I just fixed it or not. Please see the other question I have about the difference in measurements between the old and new capacitor.

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  • Lots of video with decent audio will go a lonnnng way in helping to diagnose sporadic issues. Record a couple of good and bad sessions, commenting on every observation. If possible, get temperature and pressure measurements inside and out on video.
    – bishop
    Aug 28 '20 at 6:48
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I would suggest listening to your unit when it is running , not just the fan but the compressor also. Possibly make a recording I am talking about the outside unit.

When the unit is not cooling try listening and recording again, The problem could be as easy to fix as an intermittent contactor (a contactor is a high power relay that turns on the compressor) some units have different relays for the fan and compressor so listening is important, the compressor not humming away may indicate it is “sticky” or possibly the starting cap is getting close to failure.

A cap going bad normally causes dimmed lights and hard starting it’s hard to explain the sound but it can take 10-15 seconds when normally it is up to speed in 3-5 seconds. When the start capacitor fails it may blow the fuse or circuit breaker. Or it may over heat the motor and the mother’s internal thermal overload turns it off until it cools.

If I was called for a intermittent cooling issue I usually check the cap they are a cheap fix and look at the contactor and see if it has been throwing excessive arcs. Other things like bad valves in the compressor can be the problem but if your technician put a gauge set on it that would be obvious. One of the last things of the top of my head would be the thermal expansion valve on the evaporator (inside coils) these can stick closed and prevent refrigerant from flowing so the outside unit starts pumps up to shutdown pressure then waits for a cycle restart timer 3-7 minutes on most systems. Edit: You might ask your tech if he measured the cap or inspected the contactor. (Both are in the outside unit). At this time your ears are thallus you’re best troubleshooting tool. Intermittent problems are hard to find because everything is running when we get there.

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  • I think there is no refrigerant flow between the inside unit and the compressor when it's not cooling, there is also no water draining out, I took the hose out of the pipe and put it in a bucket to test
    – amphibient
    Aug 27 '20 at 20:55
  • Are you saying that the compressor may not be running? The fan is blowing, , is there another thing that may not be working?
    – amphibient
    Aug 27 '20 at 21:00
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    @amphibient No water (technically condensate) goes together with "pipe is warm", by definition (the condensate condenses because humid air flows over the cold pipe). The thing we're trying to answer is "what parts of the system are not running?" Aug 27 '20 at 21:21
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    It is possible the compressor is faulting on startup and overheating it happens when the caps go bad or the compressor not running or the TXV sticking all 3 of these items will prevent cooling with no cooling no condensate +
    – Ed Beal
    Aug 27 '20 at 22:37
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    Hi, please check the update I just made. I confirmed it was the compressor and replaced the capacitor but not sure if that will fix it
    – amphibient
    Aug 3 at 1:16

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