Rear light Dilemma

Wobdog

Wobdog

a.k.a Mike
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I recently cleaned up my tail lights and put in LED bulbs for the running and brake lights. Everything works except the left turn signal light does not work, instead when I turn on the left turn signal or the flashers the left running light flashes. All works fine on the right.
 

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Have you tried turning on your running lights on to see which bulb lights up?
 
  • Fuse not blow
  • Grounded
  • Running light second light in- See picture.
  • I suspect I may have wired wrong, or wrong bulb is wrong place
  • Wires are - See pictures
Blue/Brown or Black stripe
Green/ Red Stripe
Blue/Green strip
Grey/White strip
Brown Ground
 

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Left rear turn directional s/b Blue with Red tracer. Do you have a single element bulb in the turn directional?

1678062975583.png

8. Turn Directional Left Front 66. Rear light cluster left a. Reversing light b. Stop light c. Turn indictor d. Rear light e. Fog light
 
Last edited:
2800 has a few differences but LH Turn is Blue/Red as mentioned. These diagrams are invaluable:

Coupe Wiring and Relays

This Thread will attempt to display the wiring legends, diagrams and relays for both euro and US versions with photos and descriptions. 2800CS Early (Feb and Jun 1970) 1) Wiper Delay: brown/black (2), green/black (2), black 2) Wiper Changeover: green/black (2), brown/red, black (2)...
e9coupe.com e9coupe.com
 
I do have a single element bulb for the flasher. I do have Blue/Red for turn Left
Turn
Left Blue/Red
Right Blue/Black
Park
Left Grey/Yellow
Right Grey/Whit
Brake
Left Green/Red
Right Green/Red
Reverse
Left Blue/Grey
Right Blue/Black
 
I would replace/add a traditional bulb for the turn indicator for test.
Case a: It works >> then you should replace the bimetallic flasher by an electronic one
Case b: It does not help >> continue with search on wiring,,,,
 
Replace the turn signals back to incandescent.

Your reflectors could use a refreshing, they seem pretty dull. There are 2 options for doing this.
Aluminum or mylar “stainless” tape available at any hardware store, usually in the heating sheet metal area. This is the easiest way. Can also mask & paint them with Chrome or Bright Aluminum (if you can find it). The Chrome paint is at auto part & hardware stores. Doing this is the best way to make all the rear lights & signals significantly brighter no matter your bulb preference.

If you have the original mechanical signal flasher, it requires specific bulb resistance to work properly. The new ‘black box’ flasher relays are expensive & will maybe last a year before failing.
 
The point on grounds relates to the grounds in the tail light assembly. If path to ground for running light has less resistance than turn signal, current for turn signal will not flow to turn signal.
 
The running light left and right circuits are independent, they even have separate fuses. They only meet at the light switch, so comparing left vs right is inconclusive.

Left front and left right running lights however are the same circuit. If the left rear running light is ON but the left front is OFF when you activate the flashers, then you have wired it wrong.

IMHO ground, ground differentials, fuses, and incandescent bulbs are all rear light colored herrings...

If both front and rear left running lights are ON when you put the flashers I would say you created a "Byzantine Failure". Then the red herrings start looking pinkish and I will eat my hat.
 
I don’t understand why people mess with factory lighting. From the factory it was fine with the exception of the lack of low beam relays which BMW itself recognized and fixed appropriately and is an easy and cheap fix for us.
The cost of the turn signal relay is ridiculous… over 200.00 from US suppliers to E105.00 at Walloth with 50.00 in shipping.

The EL electronic relay is dirt cheap and reliable- 14 bucks with free shipping from Amazon.
Just 3 wires make the connection….


BMW Hazard Flasher Relay Genuine 61.31.1.364.984 61311364984 61-31-1-364-984 61311365609 61 31 1 364 984 | Pelican Parts

Genuine Hazard Flasher Relay $206.00. Call (310)626-8765. May Qualify For FREE SHIPPING. Parts# 61 31 1 364 984 61-31-1-364-984 61.31.1.364.984 61311364984 61311365609. Bavaria, 733i, 633CSi, 630CSi, 530i, 528i, 320i, 3.0Si, 3.0S, 3.0CSi, 3.0CS, 2800CS, 2800, 2002tii, 2002, 1602.
www.pelicanparts.com
 
Napa has the relay and also an H4 socket/pigtail which works perfectly for the relay. Just did one on a '73 and the owner was shocked as he hadn't seen the indicator in the cluster for 20 years. Still working through a couple other light issues on that car but I'm hopeful a new hazard switch will fix that after looking at the wiring diagrams.

I put a new factory hazard relay in my E12 and a couple months later one of the contacts fell off inside the relay. No thanks.
 
When I first acquired my car, the high school drop out who installed the prior owner's stereo spliced into the fuse 1 circuit, pulled the 5 amp fuse and installed a 40 amp fuse in its place. When the owner then cranked up the stereo, she melted the fuse block, left side tail light assembly, and most of the wires in the left side lighting circuit. I got a tail light assembly from Peter Coomaraswamy, repaired the melted fuse block, wiring behing the fuse block, and both ends of the wiring near the light sockets, but then I had this exact same issue. With incandescent bulbs.

And it was a ground problem. The turn signal ground runs through the tail light before connecting to the metal strip that the ground wire is attached to. I added a wire from the tail light assembly to the metal strip inside the light assembly and it solved my problem. ( I also did Andrew's aluminum tape improvement at the same time.)

Not sure why this experience would be leading the discussion down the wrong path.
 
Ohmess said:
When I first acquired my car, the high school drop out who installed the prior owner's stereo spliced into the fuse 1 circuit, pulled the 5 amp fuse and installed a 40 amp fuse in its place. When the owner then cranked up the stereo, she melted the fuse block, left side tail light assembly, and most of the wires in the left side lighting circuit. I got a tail light assembly from Peter Coomaraswamy, repaired the melted fuse block, wiring behing the fuse block, and both ends of the wiring near the light sockets, but then I had this exact same issue. With incandescent bulbs.

And it was a ground problem. The turn signal ground runs through the tail light before connecting to the metal strip that the ground wire is attached to. I added a wire from the tail light assembly to the metal strip inside the light assembly and it solved my problem. ( I also did Andrew's aluminum tape improvement at the same time.)

Not sure why this experience would be leading the discussion down the wrong path.
Click to expand...
Fair point. I suggested a test to determine if he faces a simple case of miswiring, or a more complex scenario like you encountered.
 
Arde said:
Fair point. I suggested a test to determine if he faces a simple case of miswiring, or a more complex scenario like you encountered.
Click to expand...
Test for my scenario is pretty simple. Measure resistance from the side of the turn signal socket (which grounds the bulb) to the ground wire attachment point on the back of the assembly and compare to the resistance from the side of the running light wire socket to the same ground wire attachment point. Equal resistance = no problem. Higher resistance at the turn signal socket indicates a problem.

Of course, in this situation, resistance of the bulbs is probably not similar, and that alone could be causing this problem.
 
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