2007 Buick Lucerne Windshield Wiper and Pump Motor will not

I have a 2007 Buick Lucerne with rainactive automatic wipers. The other day my wipers in a very light rain started to go crazy. The wipers began to run constant at a high rate of speed and the pump motor ran constantly. It took a few minutes to drain the fluid, but then the pump motor ran for 20 minutes. The control for the wipers had no effect upon how the wipers and pump behaved. I could not turn them off. I tried shutting the car off and restarting the car. The problem did not go away. I shut off the car and pulled the fuse for the wiper motor ( I didn't realize that there was separate fuse for the pump motor) I drove home, put the fuse back in, wipers began to run crazy 2-3 minutes later. I removed the wiper fuse again. The next morning, I left the fuse out as I drove I began to here the wiper pump motor engage and run constant. I then check for and removed the fuse for the pump motor. I took it to the dealer, they put the fuses back in and are unable to recreate the problem, they tell me that the diagnostics on the modules comes back without any problems.

My question is are they missing something? What caused my wipers and pump motor to appear to be possessed?