One problem related to windshield wiper/washer switch has been reported for the 1998 GMC Sierra. The most recently reported issues are listed below.
Windshield wipers stopped and then may start at a later time. The last incident was when it stopped August 20, 2004 in a driving rain storm and we had to pull over but it soon restarted. Later the same day it stopped again and did not restart placing us in a dangerous situation. This morning it is working again.