Hb heater switch

[v8jim]

The heater on my '69 hb gt wasn't connected when I got it,there is a 4 terminal switch to the right of the colmn where the wiper and light switches are the isn't connected to anything and I'm guessing this is the heater one,it is marked 1,2,3and4 I've found the 3 wires that come from the motor under the dash. Can anyone tell me which wires got to which terminal and what goes to the fourth? Wiring isn't my strong point.