Electrical Detective Work

[Rek]

When I use the right indicator (turn signal), the front works but the rear doesn't but somethines there is a slight glow to the bulb. The left side all works.

In the right side when the front is working it stops working when the brake is pressed. Same with the hazard flashers which work apart from the rear right, but they all stop when the brake is pressed.

Things checked so far:

Rear light cluster seems to be fine.
Hazard flasher seems fine (but might not be)
Flasher unit seem to be working fine
No sign of a short, but it could be hidden
Brake light switch seems fine


Does anyone have any ideas? I think I need Hercule Poirot or someone similar.

 

[Sean Haas]

I had something similar a while back. Drove me nuts. Finally found a small, loose piece of metal in the light assembly that was causing a short between the brake light and the turn signal.

 

[Mike Goble]

Do you have all the correct bulbs?

 

[jmackro]

My first step would be to verify that the right rear light assembly is well-grounded. Does the right turn signal also quit when the headlights are turned on?

 

[Rek]

Do you have all the correct bulbs?

Yes - I think so. This is a new problem rather than a result of any work. The boot/trunk is full of stuff so it might be that the problem is there. I will check again.

 

[Rek]

My first step would be to verify that the right rear light assembly is well-grounded. Does the right turn signal also quit when the headlights are turned on?

I will do this. I do not know whether the left light stops too. I will check today.

 

[nosmonkey]

Check your earth's, if you want a spare known working light unit to test head over to mine mate

 

[Bmachine]

My first step would be to verify that the right rear light assembly is well-grounded. Does the right turn signal also quit when the headlights are turned on?

I had a very similar issue just recently. There is a ground wire that needs to be inserted inside the rear light cluster housing. It cannot be seen from the outside like the other bulb connections. You have to take the housing out. It's a good opportunity to Clean that connector from corrosion

 

[ScottAndrews]

The fact that youhave a fain glow is a tipoff thatyou have a bad connection somewhere in the lamp. Check the ground as Bmachine suggests. Also clean all the bulbs and bulb sockets to be sure they are making good contact. De-Oxit is your friend...

 

[Rek]

Found it. You were correct in that it was a faulty earth. The earth sockets in the lamps are two pieces of metal, one with a connection to the earth and the other connected to this by a copper band along the back of the light housing. There was a connection fault at the pillars which attach the two parts to the copper strip. A lot of contact cleaner and heat and I managed to get a good connection again.

Thanks for the advice and help.

 

[rsporsche]

that makes sense, the most common issue in vintage BMW is ground issues. whether in an element or the common ground loosening up. always the first place to start.