1996 Oldsmobile Bravada wipers, windshield & visibility problems

The windshield wipers on my bravada don't always work. I've taken it to a dealership and they have replaced the wiper switch and it still does the same thing. I've taken it back a couple of times and the just tightened everything up and say it is okay. But the wipers still don't work all the time. There really is no rhyme or reason, I thought I had it pinned down to when the engine got hot or when it was hot outside, but even that doesn't always hold true.

While driving, the front and rear windshield wipers worked intermittently. The failure increased with the wipers not functioning at all. The problem seemed to have been caused by an electrical circuit board or motor. The rear wipers still were not functional. The front wipers were repaired.