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  1. #1
    Join Date
    Jul 2012
    Posts
    6

    Need help - everyone seems to be stumped

    I've had two different companies come look at this "problem" and both have not been able to figure out a solution, other than just replace major components. The reason i use quotes is because the unit itself (one unit, two zones, upstairs/downstairs) is cooling just fine, even on 100+ degree days. Refrigerant levels are fine, no leaks, coil isn't frozen over, no blockage, etc. The strange behavior that is occurring, however, is that intermittently the air will just stop for a fraction of a second and then keep going like nothing happened. Some days it happens once every few minutes, other days it happens once every few hours and it is definitely not a short cycle. I can't find any way to replicate it or make it happen on purpose. Bear in mind it literally happens for a fraction of a second. Just turns off (air stops coming through the vents) and then immediately back on. The only other thing i noticed is that the unit in the attic does make an audible noise when it stops but it's so quick to come back on that it's difficult to describe it. Best i can say is that it sounds like a deep bass sound you might hear if your neighbor was playing their stereo too loud.

    I don't really know what to do since, aside from the random starting/stopping, the system seems to be working perfectly. My concern is that if i don't address it now it might turn into something major later. Has anyone heard of anything like this before? The two people i had come and look at it both said they had never seen anything like it before. Thanks in advance.

  2. #2
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,537
    What type of equipment do you have Trane, carrier etc...??? If you list this it could be helpful as most contractors know there equipment and know if there is certain problems with these matters. Does the blower on inside unit go off? What have the companies that have come out to review over the problem say. Any ideas from any of them?

    Model numbers of your equipment would be very helpful but in cases like yours without being there it will be hard to say what is or is not happening.

  3. #3
    Join Date
    Sep 2003
    Posts
    1,677
    Change the Thermostat.....It is always the thermostat

    Just Kidding

    Does the outdoor unit (condenser) stop as well as the indoor unit at the same time

    If you've been able to catch it that is.

    I would be concerned that this "stoppage" would become longer in duration and could cause you issues down the road fuses blowing, breakers tripping compressors failing etc.

    What kind of system is this just plain forced air a/c, heat pump?

  4. #4
    Join Date
    Oct 2008
    Location
    Indianapolis
    Posts
    172
    I had a call a couple of weeks ago that had the same symptoms that you are describing. The unit would make a "audible noise" as you have mentioned. In my case the audible noise was coming from the blower motor starting back up before it had come to a complete stop. Without getting into the circuity the problem was the thermostat. Changed the stat no more problems.

  5. #5
    Join Date
    Mar 2007
    Location
    NW AR
    Posts
    2,478
    Need model and serial numbers. The deep bass sound you describe immediately makes me think its an x13, which will make that sound when "braking", as they do when they shut down.

  6. #6
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,662
    Quote Originally Posted by Indy View Post
    I had a call a couple of weeks ago that had the same symptoms that you are describing. The unit would make a "audible noise" as you have mentioned. In my case the audible noise was coming from the blower motor starting back up before it had come to a complete stop. Without getting into the circuity the problem was the thermostat. Changed the stat no more problems.
    Same thing about 2 years ago. First I thought it was the capacitor, it was 3 mfd when it should have been 5. Slightly bloated and a little oily, but still functioning. But would stop running every so often, motor too hot to touch, figured going into overload. Ended up being the thermostat finally.
    I like DIY'ers. They pay better to fix.

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    The thermostat mght be worth a try. If that's the cause, allowing this to continue to occur could be very hard on your compressor.

  8. #8
    Join Date
    Jul 2012
    Posts
    6
    Wow, thanks for all the quick replies.

    Carrier System
    Model# 58STA045-12112
    Serial# 4605A21681
    Series 120
    Date of Manufacture - Nov 2006

    As far as i can tell, everything shuts off for a split second and then comes on again, but it is really hard to tell because it's so fast and so random. This has been happening for a few years now (just during the summer, i use gas for heat) but i have always ignored it since it cooled/cools just fine. As far as changing thermostats, i have two - one upstairs, one downstairs. I assume both would be worth replacing? Is this something i could do myself?

    Edit: The guys that came out to look at the system said everything was running fine. Refrigerant wasn't low, no leak, etc. Basically, they ended up suggesting not worrying about it until it wasn't cooling properly and then i would likely have to replace the Honeywell circuit board that controls the dampers, etc. (~$$$$) There was no mention of thermostats or much else for that matter.
    Last edited by jpsmith1cm; 07-16-2012 at 05:35 PM.

  9. #9
    Join Date
    Jun 2011
    Location
    Houston area
    Posts
    1,493
    Quote Originally Posted by Spurlock View Post
    Basically, they ended up suggesting not worrying about it until it wasn't cooling properly and then i would likely have to replace the Honeywell circuit board that controls the dampers, etc. (~$$$$) There was no mention of thermostats or much else for that matter.
    I'm gonna call BS on that. If it IS an X13 indoor fan motor they are notrious for these symptoms. Pull the panel off and try to take and post a pic of the motor. I can spot one in a New York minute.

    But, I'll admit this can be a very difficult problem unless the tech catches it in action. My daughter used to say "Daddy my car is acting up" and I'd do a test drive and it would would perform perfectly. Sometimes these type of intermittant problems can drive you nuts.
    Last edited by jpsmith1cm; 07-16-2012 at 05:36 PM.
    The picture in my avatar is of the Houston Ship Channel and was taken from my backyard. I like to sit outside and slap mosquitos while watching countless supertankers, barges and cargo ships of every shape and size carry all sorts of deadly toxins to and fro. It's really beautiful at times.....just don't eat the three eyed fish....

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  10. #10
    Join Date
    Oct 2008
    Location
    Indianapolis
    Posts
    172
    Quote Originally Posted by Spurlock View Post
    Wow, thanks for all the quick replies.

    Carrier System
    Model# 58STA045-12112
    Serial# 4605A21681
    Series 120
    Date of Manufacture - Nov 2006

    As far as i can tell, everything shuts off for a split second and then comes on again, but it is really hard to tell because it's so fast and so random. This has been happening for a few years now (just during the summer, i use gas for heat) but i have always ignored it since it cooled/cools just fine. As far as changing thermostats, i have two - one upstairs, one downstairs. I assume both would be worth replacing? Is this something i could do myself?

    Edit: The guys that came out to look at the system said everything was running fine. Refrigerant wasn't low, no leak, etc. Basically, they ended up suggesting not worrying about it until it wasn't cooling properly and then i would likely have to replace the Honeywell circuit board that controls the dampers, etc. (~$$$$) There was no mention of thermostats or much else for that matter.
    Since you said it was in cooling only I am leaning more towards the thermostat. Try and isolate which zone is calling for cooling when you notice the problem. If it is the thermostat at least you will know which one to change. I would have your HVAC contractor change it for you.
    Last edited by jpsmith1cm; 07-16-2012 at 05:36 PM.

  11. #11
    Join Date
    Dec 2003
    Location
    Citrus County, Florida
    Posts
    1,627
    you can try to place the thermostat fan control in the "ON" position and see if the problem continues.
    Doug

  12. #12
    Join Date
    Sep 2003
    Posts
    1,677
    Random issues can drive you nutso

    I have a 410A armstrong a/c that either the pressure switch or the thermostat turns the unit off for a second or 2 and then right back

    And it is also very random...

    So in the short term I installed a delay on make time delay relay in the condenser right before the contactor, even tho the tstat had one also to protect the compressor from short cycling too much.

    And I have ordered some tattletales and will install one on that pressure switch to see if it is the culprit or not

  13. #13
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    403

    X13, Ecm + Zoned

    If it's an x13 or ECM, and the static pressure becomes too high when only one zone damper is open, the motor will come to a full stop and restart in order to "reset" itself to the correct cfm.

    The zone dampers should be set to a minimum 25% open.

    If there's a bypass relief, check it to see if it "bounces" or "flutters" excessively.

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