wiper issue on my 85

[3x2GTO]

The wipers on my 85 K30 work fine thru all the speed including intermittent, they park fine when turned off. The problem is with the wipers off, every time you turn the key on to start the truck the wiper arms jam into the cowl vent. I removed the arms and watched the pivots, they make 4 revolutions each time the ignition key is turned on. I installed a tested wiper motor today and still have the same problem, is the switch shorted? Thanks!