Most condenser coils are loaded with pollen and dust even when you can't see it. The longest a condenser should go without cleaning is 2 years, depending on how much it operates during the summer. If your cooling season is 4 months or more, annual cleaning is an excellent idea.
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Condenser coils hardly ever
...

Most condenser coils are loaded with pollen and dust even when you can't see it. The longest a condenser should go without cleaning is 2 years, depending on how much it operates during the summer. If your cooling season is 4 months or more, annual cleaning is an excellent idea.
http://srmi.biz/Tips.Residenti...
Condenser coils hardly ever
freeze, so usually they fail because they have “died of old age” or they have suffered
severe corrosion.
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