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I just had the capacitor on my air conditioner fail. It was explained to me that the reason for this was the oil inside the capacitor got too hot, expanded, made the whole thing bulge, and no more cool air or spinning fan.

Is this is a "all parts wear out" thing? Or can misuse of an AC unit cause this sort of problem? Or can other things being wrong with the AC unit cause this sort of problem?

The main question I'm trying to answer is: How can I avoid this in the future?

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When exactly was the air conditioner built? –  Compro01 Aug 8 '13 at 14:25
    
@Compro01 I'm not sure, it came with the house. It's an XE 1000 if that helps track things down. –  Alan Storm Aug 8 '13 at 14:53
    
When did you get the house? Did the guy mention whether the capacitor had been replaced before? –  Compro01 Aug 8 '13 at 16:11
    
@Compro01 You give me too much credit :) I bought the house three and a half years ago, if there was a mention of the capacitor it's been lost in the mists of time and paperwork. –  Alan Storm Aug 8 '13 at 16:32
    
I was meaning whether the guy who did the repair mentioned if it had been replaced before. –  Compro01 Aug 8 '13 at 17:05
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3 Answers 3

up vote 5 down vote accepted

The life of electrolytic capacitors is primarily shortened by heat. Therefore ambient temperature, temperature of nearby motors, ventilation and air circulation (e.g. fan), presence of thick layers of dust, clogged grilles, excess paint, ... can be important factors.

Electrolytic capacitors are manufactured to various specifications:

  • Capacitance: e.g. 1 uF, 10000 uF
  • Voltage (maximum) e.g. 5V, 400 V
  • Lifetime e.g. 1000 hours at 80 C, 1250 hours at 150C
  • Operating Temperature e.g. 40-85, 25-150 C

By choosing a capacitor that suits your operating conditions you can ensure that you get the maximum life.

As with many things, some manufacturers produce good quality products and some low-cost manufacturers simply lie about their products' specifications. Choosing the right manufacturer may have a large influence on operational lifetime.

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According to what I can find, the XE1000 line was manufactured from about 1994 until about 2006.

If it was made in 2000 or later, it may be a victim of the capacitor plague.

Some background : From about 2000 until about 2008, various Taiwanese electronics parts manufacturers produced water-based aluminum electrolytic capacitors containing a flawed electrolyte formula. Specifically, the formula lacked the phosphate corrosion inhibitors needed to protect the aluminum anode. Without the inhibitors, instead of a stable layer of protective aluminum oxide on the anode, you instead get a buildup of aluminum hydroxide. The reaction producing that aluminum hydroxide buildup also produces hydrogen gas. Capacitors have vents to deal with that gas (as the hydroxide reaction happens even with the inhibitors, but at a much lower rate), but eventually, the rate of the reaction grows to a point where the vent is not able to vent the gas as quickly as it is being produced. The pressure then builds up to the point where the capacitor seals or casing bulges or even outright bursts. This obviously wrecks the capacitor. This failure tends to happen after about 2-3 years under most circumstances.

From about 2002 til 2010, vast numbers of computer components and other electronics suffered failures due to these capacitors. Dell initiated a recall and spent hundreds of millions of dollars replacing these capacitors which were used on the motherboards of many models of their computers and many other manufacturers implemented similar measures.

If this is the case, the failed capacitor has probably been replaced at least once before, and replaced with another such capacitor, which then failed again.

Alternatively, if it was one of the earlier units, the capacitor may simply have reached the end of its lifespan, as RedGrittyBrick suggests. Under typical conditions, a typical quality non-defective electrolytic capacitor has a lifespan of about 20 years.

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Wow, that's super interesting (or maybe I'm weird and find this historical stuff interesting). Thanks for the lesson! –  Alan Storm Aug 8 '13 at 17:38
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If the replacement capacitor seems to solve the problem then there is not much you can do. The capacitor can fail because the motor is getting old and takes more to start, small twig blocked the motored and stalled, surge/voltage spike (either from the line or bad motor's back-emf), or just it failed/life expectancy was reached.

Tl;dr, in my experience, fluke or fading motor, worth the cost of a cap or two to make sure before replacing motor/unit.

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