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