Rear washer issue

Hi I own a defender 300tdi 90 1995 plate with an original rear washer wiper switch the wipers work fine and run off the front two terminals but the rear & top terminals had no wires connected to them , my question is what are these terminals for ,I'm thinking the top terminal would connect to the pump which is earthed ?

Was your landy a truck cab at one time, hence no wires? although they may well be in the dash.
Put a tester or test bulb on and see which tab works when switch pressed in.

So ive checked for continuity between the two terminals when you press the button in for washer fluid and there is , but if you probe the terminals for power there is none , so I connected power to the top terminal which just made the wiper run continuously, so took off and connected power to back terminal and when I pressed washer button in wiper worked, so I'm thinking if I now connect the top terminal to the pump it will squirt washer fluid and wipe at the same time , so can anyone who has a 300tdi with a rear wiper switch is that how it works ie does it wipe and squit or just squit?