Slow Windshield wiper

[landriopa]

As I was driving my 63 Avanti home from the Studebaker Swap Meet in Dunkirk Friday, I caught up into a monsoon.  I quickly realized that the wipers while prefect for a light rain were no match for a heavy rain.  They work properly and reset but have only one speed.  No matter where I turn the knob, the wiper speed does not seem to increase.  Is this a wiper motor or a rheostat switch problem?

[Gunslinger]

Probably not the motor...it only does what the switch tells it do.  I would first check that the knob is tight on the shaft...it's held on by a hex screw.  That could need tightening.  The switches themselves rarely go bad but it can happen.