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  1. #1

    Question Is A/C compressor affected by outside temperatures?

    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!

  2. #2
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    Quote Originally Posted by Johnnyma45 View Post
    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!
    The O/D ambient does have an effect on the compressor, but should not cause issues with it turning on and off.

    The system may be over charged or air flow over condenser is restricted.

    A lot more data would help such as voltage, amperage, pressures, temperatures etc.

  3. #3
    ...is there an easy way to find that information? I'm not handy at all.

  4. #4
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    Quote Originally Posted by Johnnyma45 View Post
    ...is there an easy way to find that information? I'm not handy at all.
    Ya Call in a Pro!

  5. #5
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    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!!
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  6. #6
    Quote Originally Posted by Shophound View Post
    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!!
    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.

  7. #7
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    Quote Originally Posted by Johnnyma45 View Post
    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.
    it is hard to say what is wrong with the compressor, but the individual that changed to capacitor should have taken all of the measurements and posted on his service ticket.

  8. #8
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    Quote Originally Posted by Johnnyma45 View Post
    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
    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!
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9

    How to post a question and know the reviews on this website..?

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 08-06-2012 at 06:15 PM. Reason: Non AOP Member

  10. #10
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    Quote Originally Posted by mohsinrkhan86 View Post
    Congrats for your 10K posts. Now can anyone/you can help me know how can i post a question in this hbac-talk forum. I am new into it and have bunch to ask...
    Well you just posted, and you will get an Email notification each time someone responds to a post that you are subscribed to.

  11. #11
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    mohsinrkhan86

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

    You can find the rules for posting and qualifications here.

    Additional infractions may result in loss of posting privileges.


    You should review the AOP rules and site rules. I edited your post because that is the rules for this forum.

    You should look on the main forum page for a button to start a new thread.

  12. #12
    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".

  13. #13
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    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.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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