Im afraid I have run into the same problem that you have in not being able to EXACTLY place each wire in correct places on your 1990 Club Car. First of all there are different forward and reverse switches out to replace the original along with different adaptations for each for different years cart? In most cases the wires going to the S1 and S2 are hooked to the moving plate on rear of switch, and one wire goes to 1/2 battery pack for reverse HALF SPEED?
Looking at 1984-1991 Manual stock switch from back side ( From over top of Batterys )
On the lower part of F&Rswitch there are 2 terminals ( one which will be for 1/2 speed? ) ( Some years these are hooked together )
On right upper side is 1 Terminal
On the back on the moving plate are 2 terminals
I hoped someone that does the change over all the time will come on and help you out? SORRY