brake light short

Has anyone had this problem? 91 Taurus wagon-blows fuse when brake peddle depressed. I removed all bulbs, changed the switch on the peddle and changed the turn signal switch. Also unplugged the flasher. Car continues to blow the fuse. Turn signals and flashers work fine. Car starts and drives fine.No warning of the failure, lights worked fine. Stopped at a rest stop, started car and had no brake lights. Any ideas appreciated. I'm on vacation and would hate to drive 600 miles home without brake lights. Thanks.

Welcome to the forum!

Are you sure the fuse blows only when you step on the brake pedal? With all bulbs removed, did it still blow the fuse only when you pressed on the brake pedal? Did you also remove/disconnect the high-mount stop lamp?

You may want to install a test lamp in place of the fuse to save on fuses during troubleshooting. The test light bulb will light when the current draw increases. If you get basically a full intensity glow when pressing on the brake pedal, you can then go around unplugging items from the circuit until the test light no longer glows brightly when the brake pedal is pressed. At that point you've found your culprit.

-Rod

I don't have a service manual/wiring diagram for the 1991. Looking at the 1994 wiring diagram and hoping it's similar, it looks like it's probably the 15-amp fuse number 1 in the instrument panel fuse panel that's blowing. This fuse power both the multifunction switch as well as the brake light circuit. If this fuse is blowing, and the 1991 is similar to the 1994, then you should lose turn signals as well as brake lights. Also, you shouldn't be able to shift the car out of park if your 1991 has the shift lock.

-Rod

Thanks for the quick reply. The first thing I tried was removing all bulbs, and disconnecting the third light harness. I opened the rear glass at the rest stop and I thought something went wrong back there. No luck. I do have hazards, running lights and turn signals. Changing out the turn signal switch and brake switch did no good. The Chilton's manual shows the circuit going through the multi-function switch. I assume that's the turn signal switch.

The #1 fuse blows as soon as I press the peddle. I have continuity from the red wire with the green stripe to ground even after I disconnect it from the first harness I can get to under the dash. Cutting the red wire at the brake light switch allows me to press the peddle without blowing the fuse.

I have rigged a wire from the brake switch to the tail lights, but without seperating the original wire. I'm sure I'm backfeeding. I have dim brake lights now. When the running lights are on the brakes are not much brighter than the running lights. Turn signals and hazards still work until I hit the brakes, then they freeze, but the light becomes much brighter. I want to cut the original wire at the bulbs, but I believe the turn signals run through the same wire. At least I'm not blowing fuses and have usefull brake lights during the day.

There's a short somewhere from the switch to the light, I was hoping there was a switch or circuit I was overlooking.

Thanks again. DM

I finally had some time to work on this car. I spent 6 hours tracing wires this weekend. I disconnected the red wire from the brake switch and traced it back as far as I could. The Chilton's manual does not show the wiring as I found it. The red wire goes into a sealed connector of some kind. That connector has 3 more wires in it. 2 of the wires go into a harness that goes into the engine compartment. One of those wires is about 12 gauge and the other is the same gauge as the wire off of the brake switch. I believe they go into the EEC. The third wire continues into a harness under the dash, I could not trace it further. I would like to know where this wire goes. It changes color somewhere before it goes to the tail lights.

I did not find any damage to any of the wires. But now the lights work and I'm not blowing fuses. I have no idea where the problem was at. Without finding the source of the short I believe I'm still going to have problems with this car.

Can anyone explain to me why the brake light wire would go into the EEC, and how does that circuit work?

Thanks Rod for the test light idea. That will come in handy in the future. With no bulbs in the sockets my ohm meter was reading 1.193 k between the disconnected red wire at the brake switch and ground. I was expecting that circuit to be open.

DM