I bought an 87 300 SDL with a 617 diesel (from an 83 sd) transplanted into it,everything is compatible except some of the wiring harness.the problem is the A/C compressor has the older 2 prong terminal which I need to match up to the newer 3 prong terminal,(which has no current)A mercedes mechanic said the extra terminal is from the speed sensor they started using in 1986.Somehow I need to trick the AC relay on the firewall into thinking its getting a signal... Does anyone have any experience with merging these two together? Its also been hard finding a good wiring diagram,any help would be much appreciated!!