I have a 2005 Focus ZX4 sedan. It appears that the wiring between the body and trunk lid has failed which is causing several rear lighting issues including regularly blowing fuse 58 which supplies power to the left tail light and license plate lamps. I read about the hatch backs having a similar issue but nothing about the trunk wiring on a sedan. All three brake lights stay on when the fuse is good and the headlights are on. If the headlights are off, the parking lights come on with brake lights. If fuse 58 is blown, the brake lights work correctly but the left tail light and license plate bulbs don't work.

The interior button for the trunk latch hasn't worked for some time (the key works). I am not sure if this is a related issue since that wire must run through the same harness.

Am I going to have to repair my harness myself somehow or is there a replacement trunk wiring harness available? I haven't been able to find a complete harness online and I can't stand trying to work with my local Ford dealer. They don't seem to be interested in finding parts for older cars.

Thanks

 

I’m a retired aircraft technician and it was a pleasure to watch a good technician logically troubleshoot and repair a short to ground. Also scary seeing a wire in place of a fuse.



192.168.100.1 192.168.1.1

 

Even better is the challenge to find the problem and be sure that was it !
A schematic diagram is nice to have, but not always easy to get. Time was always important, but finding the problem and effecting a clean good repair was the reward.

Always nice to watch a pro do his/her work.

 

I'm sorry. Are the last two posts related to my original post? I did not use a wire to bypass a fuse at any point in locating the cause of this wiring issue.

 

Yes and no, sorry about that.

Replacing a harness can open a can of worms and I would consider that as a LAST resort.
If you don't have the equip and some background you might consider having an experienced shop check this out.
Replacing good parts can get expensive and disappointing , without actually being there to see what we are working with can be just as bad.

 

twj,
Can we be a little more specific when referring to rear lights ie.
Brake lights are STOP lights
We need to know if you are talking about rear parking lamps or rear stop lamps
It can be quite confusing to try to suggest what tests or measures to take if we don't know where we are or what we are after.
Can you help us out there,thanks.

 

I had already confirmed that the problem was in the harness that jumps from the body to the trunk lid when I started this thread. The harness at this point must flex every time the trunk lid is opened or closed. I found several wires in the harness broken and intermittently shorting to each other including the ground wire. Since I have been unable to find a new harness, I have spliced all of the wires back together. Fortunately, all of the wires had different color codes so matching and splicing was easy. My concern is that splices aren't flexible but the wiring needs to be flexible at this point. All of the lights are now working correctly but I would still like to replace this harness if I can find a new one.

Troubleshooting wiring is something I do since I am an electronics technician. Replacing broken wires and harnesses is part of my job. Splicing wires is considered a repair of last resort in my business.

In my OP I talked about rear lighting issues. The parking lights are the front parking lights, the low wattage filament in the turn signal bulb. Brake (or Stop) lights, which mean the same thing to me, are on the back of the car. Because several wires were broken at the same point, different things would happen depending on which exposed copper was touching each other at any given moment. Power was sometimes applied to the wrong wire which caused the front parking lights to come on even though the headlight switch was off. Sometimes Stop lights could stay on when the headlight switch was turned on. Sometimes a fuse would blow.

 

I realize with some electronics you don't have to contend with moving /flexing wires. What you can do when you insert a splice or series of splices is to put a loop in the wiring so the flexing is spread out and has less effect on the wiring. This can be done and also not look like a butcher job, just takes a little planning.
After your explanation , i believe you have the situation well in hand.
The problem you have covered is not as intricate as electronic work and you do have a lot more room for a decent job
.If you really want to do a professional job consider using the same gauge wire that is made for test leads and that might make the whole job a lot easier and last longer.