[VetteVet]

Pretty simple:
If you can get to the switch pull the plug off and check continuity to ground from the
off terminal. Should be infinity. Check from the low speed to ground, should be zero ohms .Check from high speed to ground, should be zero ohms.

Check from off to low, should be infinity.

check from off to high speed, should be infinity.

Check with switch in low pos, should be zero ohms to switch body, and the low and high speed terminals.

With switch in high, check for zero ohms between the high terminal to the switch body.

The push in feature grounds the washer pump. You can check this to the switch body for zero ohms.

The switch is grounded to the cab or should be.

Again I'm slow on the draw. Thanks Ray.