Diagnosing Third Brake Light issue

[speedracer92]

1987 Targa - the Third Brake light doesn’t work. Swapped bulb, cleaned leads and I am pretty confident it’s seated properly. Thoughts on what else To check? All other lights work and the entire piece is clean with no rust or corrosion on wires or leads. Thanks.

[racer]

Did you check the leads to see if power is there? Maybe a blown fuse or failing brake light switch? Do the other brake lights work? Anything else electrical not working on the car?

[speedracer92]

Originally Posted by racer

Did you check the leads to see if power is there? Maybe a blown fuse or failing brake light switch? Do the other brake lights work? Anything else electrical not working on the car?

Thanks. Other brake lights working well and except for one interior light between sun visors (it’s a Targa) which I haven’t started diagnosing yet, everything else electrical works well. That being said - completely didn’t think about checking fuses. Need to check leads - simple test light should do that right - but do i need to test both leads at same time?

[steely]

The fuse is shared by the rear brake lights and the high mounted brake lite. The power is fed to the brake switch, then to a common terminal (VS1), and from there the lites. So if your rear brakes work, I'd just check the wiring local to the hi mount.


The hi-mounted lite has some connections around the rear window defogger wiring, but I am not sure where that is exactly.

[86 911 Targa]

If you have voltage at the bulb,
check for a proper connection
at the grounding point.

Remove the bulb, and perform
a continuity check between
the ground wire and ground.

Best,

Gerry

[speedracer92]

Originally Posted by steely

The fuse is shared by the rear brake lights and the high mounted brake lite. The power is fed to the brake switch, then to a common terminal (VS1), and from there the lites. So if your rear brakes work, I'd just check the wiring local to the hi mount.

Great. Thanks. BTW< where did you get the wiring diagram you show in your post? That is very helpful.

[speedracer92]

Originally Posted by 86 911 Targa

If you have voltage at the bulb,
check for a proper connection at the grounding point. Remove the bulb, and perform
a continuity check between the ground wire and ground.

OK thanks. One of the difficulties I see in doing the check you mention above is that the way the light connects, don't see how I can check anything when its installed because the housing is flush against the glass? Don't see how I can reach anything in there....

Also, guessing i remove the back shelf and could then see the #5 switch they refer to there in the pic...

[steely]

Originally Posted by speedracer92

Great. Thanks. BTW< where did you get the wiring diagram you show in your post? That is very helpful.

I hope it helps.
My wife got them for me for xmas, I found them online (ebay ?) years ago.
I think they were extracted from a factory set of manuals and sold as a separate item.
(on edit: the wire color abbreviations are auf Deutsch - WS is white, SW is black, etc)

The Bentley manual has wiring diagrams too.

To your other comment, you might search here on Pelican to see if anyone has removed their lite. I've had mine over 10 years and have never needed to replace the bulb (but now that I have said that....).

[emac]

The first thing that gives is a bad ground

[speedracer92]

So, did a bunch of the suggestions above, and what it appears is the main issue is the way that the two tabs on the light fixture fit into the receptacle that is connected to the back dash. You can see the two tabs in the pic of the light - and the receptacle above the dash. I got it to work now sitting still but it seems a little loose. Test will be tomorrow when I drive. What I may need to do is take dash out (which I need to do to install seat belts anyway) and see if there is some tightening that can be done. Thanks for the help.