I got a 3 speed switch, 378, and was wondering how to test it to make sure it works correctly. Anyone have know how to do so? Do you need a 3 speed wiper for testing the switch?

Shop manual wiring diagrams have the info.

My Mopar has them for download

Here's a test for an ebody variable speed. Not sure if it's the same but I'm guessing it is. 0 means 0 ohms

Mike

AFAIK a "378" is the same as a "380" (variable speed switch). The following is a re-written white paper (PDF) by Slotts of JS Restoratoins .

2770380 Wiper Switch Testing

A = Brown w/ White (Bulkhead Terminal Position 1)
B = Pink
P = Blue (Bulkhead Terminal Position 5)
W = Brown (Bulkhead Terminal Position 19 – Washer Pump Motor)
F1 – Red (Bulkhead Terminal Position 2)
F2 = Green (Bulkhead Terminal Position 6)
B/U = No Connection

B to B/U = B voltage in across the internal circuit breaker.
Always on no matter what speed or off position to B/U. B/U Voltage After Circuit Breaker

The following connections should all be reading 0 ohms, except as noted, when active. Any connection combination not mentioned should not show a reading. The switch body must be grounded from side ground strap to -12v if being tested without the switch panel secured in the dash with all four screws.

In the OFF position:
B to P
A to F2
F1 to Chassis Ground

In On Low through High speed positions:
B to F1 {(0 Low) to (25 High)}
A to F1 {(0 Low) to (25 High)}
B to A
F2 to Chassis Ground

Washer Motor On – No Reading In The Off Position:
B to W
A to W
F1 to W

Thanks for the info. I will give it a shot.

Found this Youtube video on how to repair a switch (if gummed up with dirty connections). https://www.youtube.com/watch?v=CLm2OkRWV5s

I've had success rebuilding them. That video didn't address the the side terminal that you'll have to unsolder.

EWB1b - yes, no mention of that, maybe that is the "lug" that he tore. Is unsoldering that one piece straight forward?

Yup very simple. It's the silver piece in the middle of my picture, it's soldered to the outside of the case. I was surprised how little heat it actually took considering the case is a huge heat sink. I thought he broke off one of the tabs (dinks) that had to be straightened out/bent back to open up the switch. Like he said be careful with that, they're pretty soft. I had a tab/(dink) crack as I put it back together. At least it didn't break completely off.