1997 Chevy Blazer intermittent wipers go crazy

1997 Chevy Blazer 6 cyl Two Wheel Drive Automatic 155k miles

when the wipers are pulsed or put on a predetermined wipe time, they might wiper 10 times for one pulse with the switch, and the wipers do not go to the home postion. Other times they work like they should. Seems high humidity makes the circuit act up. The steady high and low wipe speeds work well all the time, it seems. Any ideas.
Thanks