when switch is off?

I had numerous problems with my 02 Trailblazer with this problem. It seems water was getting into the wiper motor and shorting it out. I think I am on my 4th motor now.

Yep. Needs a new wiper control module. About 60-70 bucks for parts and about an hour labor. Located under the cowling passenger side. Pull the fuse so you don't run em dry until you get it fixed.

I was wondering whether anyone else was having this problem too. So can I change out the module myself or is this a dealer repair issue?

If you are still under warranty, definitely a dealer issue. Otherwsie, you have to pull the wiper arms, remove the black cowling between the hood and windshield just to get at the module. The module itself is easy to replace, just remeber to seal it up like the old one was. My guess is right around $200 for a dealer to do the whole job outside of warranty.

Another thing to add to the list when it goes in today.

Mine just started doing funny things too. All my GM trucks have had problems with wipers.