GK-/GK+ are compressor speed sensor in and out, 87 is the output to the clutch, 15 is the power from switched ignition, TD causes me problems it would be engine speed on a gas model but engine speed on this diesel is on GM+, 31 is ground, T is temp sensor, KL is the comp on signal from pushbutton controller, 87k is kickdown output, VL is full thjrottle switch, and GM+ is the engine speed as stated above.
The pin numbers are 1 to 12 with #1 being terminal 31 or the right top end of your list. Pin #2 is GM+. So left to right the numbers are
11, 9, 7, 5, 3, 1
12, 10, 8, 6, 4, 2,
The common problem with the system in general is the belt slipping triggering the speed sensing relationship. On diesels there seems to be quite a few problems with the engine speed signal. This signal is prepared by the EGR module if I recall. It takes the crankshaft induced AC signal and makes a DC pulse that is used by the tach and other users. The full throttle switch also cuts the compressor and does fail. Unplugging it bypasses that problem.
For some scope patterns and general diagnostics see this article: