1994 Chevy S-10 Windshield Wipers

I've got a question about the windshield wipers on my 94 s10. They seem to work perfectly until it rains. When it rains they seem to be truely random. They may come on and wipe once and then stop for minutes or not at all. Is there a control module that I need to replace or possibly a short?

Thanks for you help,
Terry