Try cleaning the fuses in the fusebox. I lot of motor current is needed.

I expect that the switches are like those in the later models. They
have very heavy contacts that won't wear out, but they can become
corroded after years of use.

Try prying the switch panel out. Carefully pry apart the upper and
lower sections by releasing the snap in clips on the sides. You'll
find some quality contacts inside. Clean them all, reassemble, I bet
you'll be all set.

Radio shack used to sell a color tuner contact spray cleaner. You might
try to find and use something like that. Either the individual switches
or the whole panel should easily pry out.

Charles