Wiring issue!!!

[87911jon]

I'm reasonably mechanically inclined but I've always shied away from electrical stuff. How would you approach this and what tool might make it easier? 2001 Z3. On the passenger side, the brake, tail light and front light work. On the driver's side they do not. Blinker and headlights work on both sides. I swapped the rear light unit to the passenger side and it worked. Fuses are good. I'm guessing I have a break in the wiring harness on the drivers side. What's the best way to track this down? Thanks in advance! Jon

[1990C4S]

Part time trouble-shooter?

https://www.harborfreight.com/circuit-tester-set-3-piece-63612.html

and/or this:

https://www.harborfreight.com/electrical/electrician-s-tools/multimeters-testers/7-function-digital-multimeter-59434.html

At each non-functioning light 1) do you have voltage, and 2) do you have a good ground. No ground is easy to fix.

No voltage means you need to go upstream to make sure the 12V is coming from the switch, in which case you have a bad connector, or a broken wire.

Multiple 'faults' likely means the bad common ground, or a connector came undone.

[blucille]

what you want is a power probe, you can insert or complete the circuit with +12v or ground, it's pretty handy, if you understand electrical, and it sounds like--- probably not.

https://a.co/d/eP7e0g0

truth is, for all the lights to be out, you probably don't have a "break in the cable" this is pretty rare unless someone was drilling thru some stuff and hit a harness.

It's likely you have a bad ground, since all the cluster lights share a ground somewhere. Can you take some photos of what you are seeing? Most of these issues show up at one end of the car, front cluster or more likely the rear.

When was the last time they worked, what happened since?

Otherwise, google or YouTube 2001 Z3, chances are someone had the same problem and wanted to tell the world about it.

[87911jon]

Thank you!

[blucille]

lovely car, had a 99 with big motor and manual, back in the day. fun in winter in the snow and top down.

try this:

https://zroadster.org/threads/rear-lights-went-out-quick-question.37147/

I was actually hoping for a photo of the connectors to the lamp housing, I suspect that's the most common point of failure. but the thread above, it was some bad bulbs....you never know.

[William930t]

Check your trunk light wiring harness at the fold, bulb and socket, they are on the same driver's side circuit and can cause this issue.

[87911jon]

I'm at work so I can't take pictures now. The first thing I did was check the bulbs and contacts, all looked good. Next I plugged the driver's side unit into the passenger side and it worked. That's when when I knew I had an issue! Will explore more tonight. Thank you to the Pelican braintrust!

[Bob Kontak]

Originally Posted by blucille

It's likely you have a bad ground, since all the cluster lights share a ground somewhere. Can you take some photos of what you are seeing? Most of these issues show up at one end of the car, front cluster or more likely the rear.

Ground is G108 on left radiator support There is also a left parking light relay at the right firewall. I'll post some of the diagrams in a few.

[Bob Kontak]

Stack on top of each other and see if this gets you any progress. It's for the smaller engine but doubt that should matter.

[porsche tech]

Best way to check for an open circuit or a bad ground is with an ohm meter.