I recently had issues with my upstairs A/C, the outside condenser unit was shutting off randomly at random times while the internal fan continues to run. (Details in this thread: http://hvac-talk.com/vbb/showthread....s-off-randomly) In a nutshell, I had the A/C tech come back out after I recorded a video of the condenser unit emitting a high pitched screeching/whine sound. He changed out the capacitor, and we were issue-free for a week.
(http://www.youtube.com/watch?v=EJp8QTFWRxg).
This week though it has been not cooling yet again, however I've noticed this is a different issue:
1) Internal fan runs, and so does condenser fan but I do not hear the compressor on. When it is cooling, you can hear the compressor clearly.
2) It doesn't cool at a specific time, around 3-5pm, about half the days this week. Other times in the day have been fine.
3) It hasn't made the screeching sound again.
I feel like the compressor is starting to fail, and maybe the capacitor issues from before which affected the fan, in turn put more wear on the compressor. We have had 104-106+ high temps all week...does the compressor ever fail in relation to the outside temp?
FYI I keep it at 85 deg during the day and 78 at around 5pm. On the weekends (which has followed the afternoon failing pattern) I keep it at 78 all day.
Thanks!
...is there an easy way to find that information? I'm not handy at all.
Condenser fan motor stalled out, compressor went into bypass, finally cut out on internal overload...high pitched squeal afterward was bypass still open until pressures equalized a bit. Then it stopped and left you with silence.
Tech may have changed capacitor for fan motor out but the motor itself is probably bad.
Post 10,000...woo hoo!!
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Hah, congrats! So, if the condenser fan is still working right now when the compressor is off (and no coolness) would this fix my current issue? And, I do plan to call a tech, I just don't want a repeat of my previous tech who was unable to diagnose anything if it was blowing cold at the moment.
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Last edited by jpsmith1cm; 08-06-2012 at 06:15 PM. Reason: Non AOP Member
mohsinrkhan86
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Often I can spot a condenser fan motor showing signs of impending death. Lateral play in the motor shaft. Amp draw excessive. Bearings feeling a bit stiff with the motor de-energized. Imbalanced fan blades. Etc. A tech need not wait for the thing to fail in order to look for these signs.
While I have seen videos of fan blades where they appear to be turning slowly due to the frame rate of the camera, in your case it was obvious the blades were not turning at all! That is NOT GOOD!
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
So to clarify, the fan is spinning well right now. The video was from the previous issue (which the capacitor fix took care of). It has not made that sound (and the fan has been working well) since the fix. If the motor is still bad, would it cause the current issue of shutting off the compressor only during a couple of the afternoon hours?
OK, I now caught the time sequence...sorry I missed it earlier. I was completely focused on that video.
As to your current problem, your previous problem may have led to the one you have now. The compressor motor in your video stopped running only when the internal overload inside the compressor opened. This was because the fan had stopped running. You then had the tech fix the fan. And now the unit cools except in the hottest part of the day.
Which tells me that the internal overload inside the compressor may have been weakened by your previous episodes of the fan motor locking up and causing the compressor to become very hot.
If the outdoor coils are dirty, you might try getting those cleaned to see if you can coast through the hot afternoons without the compressor cutting out. If they are clean, and the refrigerant charge is right, you may be on the hook for a new compressor or unit.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Thanks Shophound, that's what I suspected. I had a tech sent by my home warranty company and after watching the video, he stopped at fixing the fan. I will look to clean the coils and hope that that will do it.
If I do have another tech come out and I explain the issue, are they typically able to detect a weakened/dying compressor if that is indeed the problem? I'd like to guide them so there's not a repeat of the last time, when he didn't find anything due to it "working".
There are tests available that can inform a person how healthy a compressor might be, but the effectiveness of those tests toward this end depend on at least two factors: a) interpreting the results of the tests correctly, and b) end user willing to pay for the tests if an extra charge on top of a service call is presented.
So what are the tests?
a) Megohmmeter - aka "megger", not often used in residential work but can inform the tester as to the health of the compressor motor windings.
b) Acid and moisture test - informs the tester if the oil in the system is acidic and/or contains moisture. Acids form in compressor oil either due to moisture or excessive heat, or both. Elevated levels can sometimes be managed by changing the liquid line drier in the system.
In your case, if the internal overload has weakened due to the recent stress it suffered from the failed fan motor, you could also have elevated acidic levels in the compressor oil. Typically, not many homeowners are willing to pay for efforts to prolong the life of a compressor potentially at risk, but some may. From that point it's a matter of finding a tech who can properly administer and interpret the tests, and inform you, the end user, what those tests indicate as to the health of your compressor.
This is why I recommend for you to ensure the condenser coils are clean. You want to reduce stress on the compressor by enabling it to get rid of heat more effectively. That's what clean coils can do, and may enable you to get through the hot afternoons without the compressor cutting out on overload.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Do not let anyone use a power washer to clean your condenser. Power shut off and as you've described is best.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Thanks for the continued help Shophound, it is greatly appreciated. On Tuesday the condenser shut off once more, a bit later in the day (6:30-7:30pm) but still followiing the high temp pattern. I'll wash it this weekend and hope for the best.