Dash had to come apart to repair some wires in main harness. There are 4 separate brown wires; one of them I know goes to the wiper motor switch. Two go to the washer pump switch. The washer switch is a two post switch. Which wire goes on which post of the washer switch? Does it make a difference? If they go on the wrong post will I have another melt down?

They can plug on either way.

Where does the fourth wire go? To the wiper motor switch?

Do you have 2 or 3 speed wipers? If 2 speed one wire is not used.

I don't know. The wiper motor switch has four positions and 7 terminals on the back so I'm going to assume its a three speed: off, slow med, high?

On the washer switch one wire goes to the pump and other is just a short jumper from the washer switch to the corner of the wiper switch where it gets its power from. So that's 3 of your 4. The last is on the switch to to motor.

So for the three wires (2 pump switch, 1 to wiper motor switch) It makes no difference which wire goes where as long as all three wires are hooked up.