Windshield Wipers

I have a '97 Chevy Silverado 2500. I hae 142K miles on it. The problem I have is that the windshield wipers sometimes work and sometimes they don’t. Mostly they don’t work when it begins to rain and when I turn them on I can hear a humming noise but they do not move. I have checked the splines on the wipers and they are ok. Someone told me that is a sensor that has gone bad. Is this true?

The wiper motor pulse board module on these models are prone to failure due to bad solder joints. I would have that checked first of all. The wiper motor could be faulty but the wiper motor pulse board module is the most likely culprit.