You should also check the solenoids located in the right side of the center console. I think they are called change-over valves. They apply the vacuum going to the elements and eventually burn out. I tested all mine and replaced 3 bad ones.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma