Can anyone explain how to test a 3-speed wiper switch. Or maybe post a link for it? My wipers do work in all three positions, but does not speed up to highest speed. Thanks!

Interesting, mine is exactly the same.

I hope we can work our way through it then!
Just went to the garage and took the switch apart and cleaned it. Everything looked good inside it and the ground strap-to housing is ok. I tested it with an ohm meter between every terminal in all positions both before and after I cleaned it and nothing changed. I resently had the wiper motor apart because it did not stop due to cracked insolation on the wires that run into the motor and also a fried terminal at the bulkhead connector. I cleaned the motor wich looked to be in pretty good shape and put new insolation on the wires. It runs smooth and quiet now and returns to correct stop position as it should.Only problem is that I am missing the highest speed. Maybe the problem is in the wiring.
Maybe I should test the motor too. Is there any good way to run the motor straight from the battery to test all speeds?

Testing a 3-speed wiper system
The 3 speed wiper system controls the speed by use of a resister in the switch, not in the motor. The switch also reverses the current to the motor in the "off" position, which causes the motor to seek the "home" position. There is also a circuit breaker built into the switch to protect the circuitry.
Testing the switch
There is a test for the switch that can be done with a continuity tester or an ohmeter. To do this test, on the back of the switch, the terminals are marked with an"A", "B", "B/U", "F1", "F2", "P" and "R1". In the tests, "Ground" is the switch casing.
While in the "Off" position there should be continuity between
B to B/U
B/U to P
A to F2
F1 to Ground
"LOW"
B to B/U
B/U to A
A to F1
F2 to ground
P - open
"Medium"
B to B/U
B/U to A
A to R1
F2 to ground
P - open
"HIGH"
B to B/U
B/U to A
F2 to ground
P - open
Testing the motor
The motor only has two speeds, high and low. The medium speed is a variable speed, which is configured by the switch varying the voltage to the motor.
"Low"
Connect the motor housing and the green wire to ground
Bridge the brown and red wires
Connect either the brown or red wires to 12v
Motor should turn slowly
"High"
Conect the motor housing and the green wire to ground
Connect the brown wire to 12v
Motor should turn fast
"Park"
Connect the motor housing and the red wire to ground
Bridge the brown and green wires
Connect the blue wire to 12v
Motor should turn backward, then stop in park position

WOW! Thanks John69RR! Exactly what I was looking for!
I'll do some more testing but lets assume the switch and wiring is good, what can cause a motor to not run at high speed? I could not find any broken wires inside the motor.

Tested the switch like you suggested and everything matches except for one thing: There is no contact between R1 and A in "medium position. In fact the R1 is left out in all positions. That doesn't seem right.
I don't know why this happends because everything inside the switch seem to be in good shape and the four contactors and springs operate properly.

Am I right that R1 gets current from the windshield washer switch just to run the wipers when the washer switch is engaged? Should this issue have anything to do with the missing high speed? I don't think so, but I might be wrong...

I will have to check. I had those tips saved from an old post. Maybe Jules will see this and help.

Thanks for your will to help!
I just performed the motor test and it runs slow at step 1 but only a tad faster in step 2. Still it seems ok. It makes a little different sound in step 2 and will propably run faster when the car runs and charges..I hope.
Still wonder why R1 don't get any connections.

Maybe this will help. You might PM Jules the wiperman if the issue continues.
http://www.valiant.org/electrical-diagrams.html
Are you refering to brown wire from the switch? That wire should be the "hot" lead for the washer, not the "hot" lead for the wiper switch.
http://www.mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerA.JPG
http://www.mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerB.JPG

Thanks! The wipers runs faster in position 2 and 3 but the difference between 2 and 3 is almost not notisable. Is this normal?