Take switch off and plug it back in. If you aren't sure how to measure voltage drop. Stick the probs from your dvom into pin 2 and 3 and apply the circuit. Anything over .5v is excessive. Your measuring the difference in voltage between the 2 terminals. The reading you get is the amount voltage the switch is consuming. A switch is not suppose to consume any voltage, its just a switch, not a device. I've had brake light issues with my Galant also. Mine turned out to be the main power wire going to the tail lights, having too much resistance and kept popping the fuses. Resistance jacks up your amperage.