Questions and Answers

Lincoln Mark III Brake Lights Q. Mr. Ciulla, I have a 1971 Lincoln Mark III with an electrical problem, (go figure). The problem I am having, and can't seem to figure out, is with the brake lights. As soon as I turn the key to the on position, the 3 amp fuse for the brake lights blows. I replaced the ignition switch, and still have the problem.

There is a green wire with red slashes on it that runs to the brake light switch that is getting 12+ volts to it. I've tried following the wire but can't seem to figure out where it goes. If I hook my Multi meter to the brake light fuse connection it is registering 12-14 volts, depending whether the car is running or not. Obviously something is causing this problem, but I can't seem to figure it out. I cannot find any bare or shorted out wires anywhere. Can you give me some ideas?

Thanks,
Dave

A. Okay Dave, this is a very basic system. First off there should be a 10 or 15 amp fuse in there, not a 3 amp.

Take all the brake light bulbs out and make sure they are all 1157 bulbs. now put a fuse in and see if it blows. If it doesn't, then you have a bad bulb.

If it does blow, then there is a short somewhere in the system. Unplug the brake light switch and see if it blows, if not then it's a bad brake light switch or wiring from the switch to the rear. If it does then there is a short between the fuse and brake light switch.