Ok, I have a very weird problem that I simply cannot figure out the root cause of.

My passenger side tail light is out (not the brake light, the light that goes on when the headlights are on.... brake light works fine). I bought a new bulb and I know that isnt the problem.

Here is where it gets weird..... I took the passenger side tail light assembly out of the car (the entire thing) and plugged it in to the drivers side tail light harness and it works fine. I took the drivers side tail light out and plugged into the passenger side harness, it works fine. This tells me two things; 1, that the passenger side harness works and 2, that the passenger side tail light works.

BUT when I plug the passenger side tail light into the passenger side harness (the way it is supposed to be) the tail light does NOT work. What in the world is going on? I have no clue why this is happening. Anyone have any ideas?

check the trunk wire. that goes from chasis to trunk alot of e36's are reported to have wires kinked too much and shield worn and short circuited. open up and check.

kingston.

checked it.... wiring appears to be fine.


Besides.... if it was a wiring issue, I dont think the drivers side light would have worked in the passenger side harness.

it happended on my car that way on my 1994 325i it looked fine but i stripped it near the center is where some of the wires were short circuit. other than that i have clue

kingston

i was gonna say a fuse issue from reading the title..but i am stumped as well

This has got to be a trick question.....this one takes the cake.

tell me about it, I am totally stumped.

Is it the whole tail light or just one of the bulbs not working? If it's just one of the bulbs it could be a bad contact in the socket.

i may sound crazy but this was the case with me...



its your head light switch. most likely. is the turn dial loose or anything

sounds like an intermittent problem, when either you moved the bad light to the good connector or the good light to the bad connector you happend to catch it while it was working and therefore did not see the problem. I would repeat what you did but in each case wiggle, shake, harass all connections and wires as much as possible and watch for flickering or some indication of a weak connection.

VE

Is it the whole tail light or just one of the bulbs not working? If it's just one of the bulbs it could be a bad contact in the socket.

Read the first post again.... you'll see why that cant be the case.



I am SO stumped on this. :help

There must be a loose connection somewhere.
Play with the harness.

ok I did the little swap and check again last night and FOR SURE the problem is exactly how I describe it.....

pass tail light in pass harness NO WORK

pass tail light in drivers harness IT WORKS (this means that the light itself and the bulb are good)

Drivers light in pass harness IT WORKS (this means that the passenger side harness does indeed work)

So.... BOTH the light AND the harness are good. But when you plug in the passenger light into the passenger harness the dam thing doesnt work (just the tail light.... but brake and turn signals work)


Heeeeeelllllppppp :(

You are assuming (by plugging the other light in and it works) that there
is not a problem with the connections. And so you will turn in a circle forever,
ignoring even the correct answer which has already been posted above.

Electrical guru often say: voltmeter is your friend. Only when you use one,
will you find your problem.

OK enough with the funny stuff. Dude, I've seen weirder crap in a lab than
you can even imagine. And I only work on designing ICs for a living.
Complex stuff like medicine.... those guys are guessing at the best of times.

Get a meter though and start measuring. You'll figure it out in 2 minutes.
It's only a connector that is busted. Until then you'll just continue running
in circles with your faulty logic (for example - what if there is a failure in a
connector where it grabs the driver side properly but not he passenger
side).

FWIW, I think the post about the intermittent ground connection is the
correct answer.

The thing is I dont know what I am looking for with the voltmeter.... I dont know what values are expected.... not sure which wire is which and what parameters it should have.


Where would you start?

Check if the front right parking light is out as well, most likely it is. The left and right side parking lights are on different circuits. The problem is the head light switch. Either buy a new one or take it out (easy) and spray WD40, yes WD40, on it and keep switching it on and off to clean the contacts. You should be OK after that, mine has been good for 3yrs after the WD40 cleaning. Also it is a dangerous condition, high resistance contacts generate heat. Easy fix.

It may sound crazy, but just for shits & giggles, check fuse # 37. I had a similar problem and it turned out to be that fuse.

Probably just shooting in the dark, but it can't hurt.

Fuses are good, that was the first thing I checked. Man, I WISH it was just a fuse :(

Dammit!!!

Good luck, man. I wish I had some reasonable advice for you....

The thing is I dont know what I am looking for with the voltmeter.... I dont know what values are expected.... not sure which wire is which and what parameters it should have.


Where would you start?

You are looking not for voltage or amperage, but for continuity.
That means you can use a simple test light or a meter set to resistance.
The light requires current to flow so you have to have the circuit energized.
A meter can be used with open circuit. That means you can leave the ignition off.
Infinite resistance means you have an open circuit at the test points.
Any other reading means you have connection.

Clean the headlight switch as recommended, if you don't find the source of your problem in the harness or light assy.

I started doing a continuity test last week.... checked all the bulbs, the bulb holders, and the sockets. When I started to test the harness plug and where it plugs into the tail light I realized that I wasnt sure which ones were supposed to be open/giving me a signal.

I would be infinitely grateful to anyone who could tell me which pins in particular I should be checking. I have already been pulled over twice at night for having a tail light out.... the cops dont care about my little problem and are going to ticket me next time.... needless to say I have got to get this figured out soon.

This is a bit mind boggling.

You can look at the Bentley schematics/diagrams to find that harness plug.
The pins should be numbered.
Gnds are brown (brn).
Or you can look at the trace in the housing and see where all the paths go.

Did you check your headlight switch yet?

checking in the morning... What exactly should I be looking for? It all seems to work properly.... Replaced it about a year ago with a new unit.

checking in the morning... What exactly should I be looking for? It all seems to work properly.... Replaced it about a year ago with a new unit.

Corrosion, dirt...it's dificult for me to see that the switch would be the problem since the other end works with the driver's bulb, but not the passenger side bulb.
It's more logical for the connector or pin to be the problem.
Still, what is there to lose? Takes a couple of minutes to check.

When you say you checked the Trunk Harness...did you just eyeball it? Or did you cut open the protective sheath and look at the individual wires inside?

I cut mine open last year...found 5+ wires with exposed insulation, and 2 that had broken. BMW used pretty crappy wire in there. I respliced the bad ones, wrapped electrical tape around it and its been ok...though I know I'll have to get back into it and fix them all at some point. Its a fire hazard...should have been a class action suit long ago. At least I keep my fire ext close by in the trunk.....

I pulled out the grommet and pulled the protective sheath up into a bunch, ex
exposing 5"+ of the wire, all looked perfect.

well I took th switch out and everything seem ok.... not really sure what I was looking for though :(

Did you switch the bulb and socket from one side to the other or just the bulb?
I know you said you tried switching the housings and have replaced the bulb.
My thinking is similar to wayn325's.
You plug the harness into the opposite housing and it works, but the matched side housing light doesn't.
I think this points to the housing socket for the harness or the connector.
Only thing is, it would seem easy to find the problem by fiddling with the connector.

I swapped the bulbs, the bulb holders, AND the tail lights.... i tried every single possible combination I think. I am starting to think it is something to do with the connectors...

I noticed that the drivers side and passenger side connectors, while the same size, have a different number of pins and sockets. The drivers side has one more than does the passenger... one in the middle (out of two) is missing while the passenger side has both pins missing. I *think is it supposed to be this way because the drivers side socket has a metal receptor fin the female end where that "extra" pin is. The passenger side has no such female part to accommodate the male pin (because it doesnt exist on the passenger side).

xjeeper has proven that the right side bulb and socket are OK by swapping according to the initial post. The left and right side PARKING light circuits are separate on BMW and Mercedes. The reason 4 this is so when parking the parking lights closest to traffic can be illuminated to avoid a drive hitting your car (US cars do not utilize this feature). It seems like the only logical conclusion is the switch. There is no relay for parking lights, only headlights, thats why it seems the head light switch is the problem. Seeing no corrosion on the plug connector is good but the problem will usually lie inside the switch housing at the contact points. Those cannot be seen.

Either find a loaner switch that is known to be good, take it out and cycle it many time to clean off carbon build up, or try to clean the contacts with a cleaner pointed inside the plastic housing where the contact are.

There must be some kind of saying, or if not there should be, if weird woo-hoo twilight zone (pun not really intended) electrical stuff happens, check the ground for real

Something kinda like this happened to me with a '95 E38, turned out the ground connection had just a little corrosion on it, but enough I guess
The hard part was finding this out
Cleaned the contact and no more brake light bingo

Good luck

Does anyone have a wiring schematic? I need to find out which wire does what.... Thanks!!