If you put 12v direct to the fan with correct polarity and it didn't work, you probably need a new one. More often than not, the fans are bad by now. I've had to replace the one on my '95 last year. There are posts about replacement fans.
Fan wiring, Violet/Yellow +12v, Brown- ground.
There is a "test" sequence that you can do to check the operation of the fan relay/fan circuit. You should be able to find it in the stickies section.
The fan relay is controlled by the motronic, and the temperature is measured by the sensor mounted behind the fan on the small coolant riser tube bolted to the block. Power for the fan relay should be from fuse #7
You can check and see if you have +12v at the temp gauge on green/black. (key on, kill switch on, side stand up, engine off)
Wires at the gauge:
Green/Black- +12 in from fuse #1,
Black- +12 out from gauge to temperature sensor at water pump,
Brown- ground for backlight
Grey/Blue- +12 for backlight.