tail light short

[long tall eta]

guys, overhead panel indicated tail lights out. when checked, right side tail not working. fuse blown. for shits and giggles i dropped a 10 then a 15 amp fuse in and as soon as inserted both blew. wires to tail lens look good and intact and untaped harness as far as left side lens. fuse 23 controls right tail, marker, and license plate bulbs. my next ploy is license plate light but waiting for PB blaster to finish it's work. question is, are there any other trouble spots ie, week links running forward in the harness that could be causing this short?


UPDATE;
so i disconnected the rear light check relay and popped in a new fuse 7.5 amp into slot 23 and it pops immediately. am i correct in assuming that the short is then north or upstream from the relay? if so, with the wire harness being electrical taped insulated for the entire length, what are the chances that the right side tail light wire broke inside the tape AND is touching something metal to create the short? could it be in the fuse box? is it possible it could be the headlight switch itself? again, everything works except for the right tail, license plate and right marker lights.

[tim88325is]

Well, I learned that the front wiring harness to the lights and windshield washer pump can get "chopped" up by 20+ years of lying on sheet metal seams with flanges that stick up and such. After an extended time frame, the insulation gets brittle and pressure of making a turn or bumping against a sheet metal edge eventually shorts it out.

I would try to peel back any wrapping at junctions or suspected areas and look for damaged wire insulation.

Good luck!!

[long tall eta]

please see updated original post.

[long tall eta]

Well, I learned that the front wiring harness to the lights and windshield washer pump can get "chopped" up by 20+ years of lying on sheet metal seams with flanges that stick up and such. After an extended time frame, the insulation gets brittle and pressure of making a turn or bumping against a sheet metal edge eventually shorts it out.

I would try to peel back any wrapping at junctions or suspected areas and look for damaged wire insulation.

Good luck!!

but even if wire insulation was damaged, it would still need to come in contact with a metal surface to blow the fuse. if it was just a broken connection it would just be a not working condition correct?

[e30onBBSs]

It's possible the wire is shorting to an accompanying wire in the harness. Pull out your meter and start checking shit.

You are right about "a broken connection" this would be an open circuit not a short circuit. An open circuit is where everything doesn't function- and like you did you would check the fuses and other connections in the circuit first. If the circuit keeps popping the fuse, there is an excess of amperes flowing through the circuit, telling you you do in fact have a short circuit not an open circuit.

Research and get comfortable with ohms, amps, resistance, volts, etc and create a diagnostic plan to figure it out

[tim88325is]

Right, if the insulation is deteriorating on one wire, the others are close behind. I just had to repair my one fog light, wire and insulation right outside of the connector just gave up after 30 years of slight flexing.

You have the electrical manual right?

http://wedophones.com/Manuals/BMW/

[long tall eta]

really hate electrical gremlins. so, am i correct in saying that for the right side rear parking, license, and side marker lights that the green/grey wire from the fuse box to the switch is always hot and sends current to the rear lights when the switch is pulled on? so power is always in the switch and gets sent rearward when contact in switch is made. the fuse does not blow until the switch is pulled so does that mean that the short is down stream from the switch? I've tried a known working switch and rear light relay (the one in the trunk)and still blowing fuses. pulled the back seat and nothing looks to be in bad shape, nothing exposed or damaged.
question, could a short in the overhead check panel or associated wiring be the cause?

[long tall eta]

problem solved, well kind of. right before the brain challenging, confusing, tail light problem i had pulled the aftermarket radio out cause the co axle cable needed splicing. after i drank a 12 pack, went to the animal shelter and picked up a couple sacrificial cats i settled down and pulled the radio back out. there was a couple old non taped wires from the original radio along with a couple unknown others. tided everything up and that's right, you guessed it, everything running hot straight and normal again. i must say i have well over 430k on the car with original engine, even the head gasket hasn't been changed unless it was done under 200k before i got her. stamped cam gear and all. this was the first electrical problem I've had. starter, alternator[IMG]IMG_20140401_161752 by robert_elliott54, on Flickr[/IMG] all original. shows you what an eta can do with regular 20/50 quality oil changes and timing belts done on time.

[tim88325is]

I did notice that not all the taillight wires went through the relay on the earlier models, so you never know until you see a schematic.

Was one of the wires you cleaned up green/grey?

Looks great!

[long tall eta]

I did notice that not all the taillight wires went through the relay on the earlier models, so you never know until you see a schematic.

Was one of the wires you cleaned up green/grey?

Looks great!

the gr gy go from the fuse box to the headlight switch then they turn to red gy until they exit the relay in the trunk where they turn back to gr gy.