hippy - mechanical gauges have a sender wire that sends a signal mechanically (heats a wire in the case of a temp gauge) to the sensor in the gauge, an electrical gauge has the sensor at the point where your measuring whatever it is your measuring, and sends a signal via electrical wire to the gauge. basically, electrical has the sensor in your engine bay and mechanical has the sensor in the gauge itself. hope that made sense. my mechanic told me that if you want to race your car you wont get past scruiteneering with mechanical gauges.....
Ross