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  1. #1
    Join Date
    Jun 2004
    Posts
    956
    What is the main cause of death for ac dual caps, or caps in general?

    Found three blistered yesterday, systems in spec

  2. #2
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Capacitors deteroriate over time. There are 3 general factors in order of significance:

    1. Age
    2. Temperature
    3. Overvoltage

    Any of these factors will accelerate failure. Most failures are a result of the dielectric material (an insulator) in the cap starting to leak some current. This results in internal heating, and either a short circuit in the cap will occur, or the current conduction and heat can sometimes burn out a conduction path in the capacitor, so it becomes an open circuit (no capacitance) or occasionally the excess internal heat causes it to vent (most have a built in vent device) or in a worst case explode.

    paul

  3. #3
    Join Date
    Jun 2004
    Posts
    956
    thanks tec, i figured age was the culprit on these but thought id ask the question anyway

  4. #4
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    voltage spikes

  5. #5
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    Mexico

    Ive cut a few of the swollen ones open, many of them the dielectric fluid had hardened up and caused the cap to overheat and swell, GE caps suck...period

  6. #6
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,763
    Two words for me...Mexico and China.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  7. #7
    Join Date
    Jun 2001
    Posts
    3,910
    And York capacitors in Lennox HS29's. Go figure.

  8. #8
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Most times I find a bad run cap, the condensor coil is dirty. Heat kills them, plugged up condensor coil causes the unit to run hotter, and the higeher amperage also causes the run cap to generate more heat internally.

    All these run caps coming in units these days are very small, wich gives them less surface area to reject heat from, and less mass to heat up during the on cycles, so they run hotter. Toss in any condition that gives them less than ideal ability to cool off and *POP* goes the top.

    I find the run caps with the plastic housings to be the most reliable by far as a replacement cap.

    Some units with scroll compressors are using 60 and 80 f run caps that are very small. I like to replace them with two 30f or two 40f run caps in parallel.
    This splits the heat generation between 2 caps, each of wich is usually physically larger than the origonal, giving much more reliable operation.

    I replace far more run capacitors every year than I replace any other single type of part.
    If more government is the answer, then it's a really stupid question.

  9. #9
    Join Date
    Jan 2005
    Posts
    109
    That was my call today. HO called and said AC not working. Run cap looked like it was ready to pop. What run caps do you guys carry in your trucks?

  10. #10

    GE of course....

    Originally posted by oilman52
    That was my call today. HO called and said AC not working. Run cap looked like it was ready to pop. What run caps do you guys carry in your trucks?
    Planned part replacements...
    AllTemp Heating & Cooling

  11. #11
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    Originally posted by oilman52
    What run caps do you guys carry in your trucks?
    One 4, four 5's, two of everything from 7.5 through 60, one 80 and two rather expensive but handy universals. I HATE running to the wholesaler for parts that cost nothing.

  12. #12
    Join Date
    Mar 2003
    Location
    North St Paul MN
    Posts
    858
    [i] I like to replace them with two 30f or two 40f run caps in parallel.[/B]
    Don't you mean in series, or have I been doing in wrong.
    I'd rather have a bottle in front of me, than a frontal lobotomy.

  13. #13
    Join Date
    Jul 2001
    Location
    Anderson,SC
    Posts
    997
    You been doing in wrong. Caps in parallel add. NATE question # 56.

    STUD

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