Our house/ AC system is 2 1/2 years old. We tried to fire up the AC this week to be sure it was functioning and it was fried. The tech came today and advised that the contacts on the switch unit were completely corroded from exposure to moisture from our power venter, which is located about three feet away from the condenser. My sister's AC suffered the same fate last year. We will be getting a cover for the condenser until we can get the power vent moved. The tech also told us that another common problem they see is mice making homes in the condenser units and eating the wires, as soon as one year after the initial install. Thought this might be helpful info to pass along to anyone with central AC.
It isn't a good idea to run vents anywhere near electrical components. It also isn't a good idea to have them near you gas meter, electric meter, or cable entry. Watch out for dryer vents as well, the chlorine from bleach that may not have been totally washed out makes the exhaust more toxic.
I ended up with a mouse in my central a/c this spring when I went to turn it on...luckily for me anyways, he electrocuted himself before he had a chance to sharpen his teeth on anything. Still had to clean up some things, but it worked.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013