Electrical – What can cause the capacitor in an air conditioner to fail


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?

Best Answer

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.