How do I find the short in my 300 SD?It starts to show up when I put a blinker on andthe speedometer needle starts to bounce wildly.Shortly after that I have no lights and am stranded.The last thing that happened was my condensor fan went on when it was not needed and would not shut off untilled I pulled the plug on it.[X(]

 

Does it blow the fuse after that happens? It doesn't sound like a short so much as a bad ground. Unplug all the connections to your dash and instrument cluster and plug them back in again in order to clean them off and reseat the grounds.

As far as the condensor fan, that does sound like a short. Unplug the connections and check the resistance across the switch on your a/c drier while the system is off. It should be infinite (open circuit). When you turn on the a/c on high/full/max you should have 0 resistance across it. If the problem is not there, or the fan turns on when you have those connections unplugged, you're going to have to trace those wires back as well as the wires from the fan motor itself and see where they are jumping.