Froggy shark

Hi Folks!

Need your help on that spot:
I bought a third brake light on ebay USA, a long time ago, and I'm about to stick it under the rear hatch (at last).

Every part is in place, now's the time to plug the right cable at the right place.

The ebay seller wasn't supplying the connecting wire, so I use a plain one (twin wire), made for loudspeakers. I guess an electrical wire is an electrical wire...

As this optional equipment is more commonly used on your side of the ocean, I sincerely hope one of you has made this wiring himself, and is willing to share his experience with me. Any pics is welcome!

Cheers,

Michel
http://monsite.wanadoo.fr/culte928

Alan

Stock there is flat wiring loom that includes the center brake light and the defrost/defogger element and rear hatch interior lighting. You might look to see if you have any spares in this loom - on the car side it runs down the passenger (LHD) B-Pillar.

The center brake light is connected in parallel to the right brake light.

Alan

Froggy shark

Hi Alan!

Thank you so much for your reply!

As I'm on my way for a rear antenna withdrawal, I removed the roof interior trim: on the pics below (sorry for the poor quality... ), there's a wiring loom, I guess this is where I have to connect the wire.

[img=http://img379.imageshack.us/img379/9650/3107080001at8.th.jpg]

[img=http://img111.imageshack.us/img111/4210/3107080002lw5.th.jpg]


Please correct me if I'm wrong, I'm a kind of reluctant with anything dealing with electricity

Cheers,

Michel
http://monsite.wanadoo.fr/culte928

Alan

Yes that is the loom - on a car with center brake light installed it will be part of this loom - I assume all cars (of the right vintage) have the same loom and the wires for the brake light are simply not connected. Its quite likely the connection to the right side brake lamp is already made - but it may not be...

It is an 8 pin (T11) connector & 8 wire loom:

Pin Function
1 Rear Screen Defrost Heater Element
2 Rear Screen Defrost Heater Element
3 Ground (stop light & interior lights)
4 Interior Lights Fused Power
5 Interior Lights Switched Ground
6 Rear Screen Defrost Heater Element
7 Brake light Positive Feed
8 Unused

So you can connect the groung the brown wire on the interior light switch - but you need to connect to pin 7 of the connector for the stop light positive feed.

I'm not sure it is completely plug & play - you may find you get stop light failure errors when its connected - I'm just not sure if there was a different config of bulb monitor for this usage case.

Alan

Froggy shark

Three months later, guess who's back?

According to Alan's advices, I've found the loose plug that I suppose is dedicated to light my 3rd barke light, which is now in place.

But my wiring is no good : I've burned the fuse #25, as everybody knows, has "Diagnostic Connector,Current Pulse-Tailgate, Interior lights" as a nickname.

No more computer in the pod, no more hatch release, but everything's allright now, with a brand new fuse

Could someone help me with the right wiring, ground, etc?

Big drawing with flashy colors would definitely help...

Cheers,

Michel
http://monsite.wanadoo.fr/culte928

Alan

Well it sounds like you may be connecting another 21W bulb to the interior lights then... I think you will need to see what each pin of that connector does. The 'chinese menu' should be the things I had listed - but use a DMM to determine what pin does what - maybe they are remaped in your car... try to find one that is active with brakes only...

Unfortunately since it wasn't designed to have this light you may need a little sleuthing - not sure how different the ROW looms are - I would have expected them to be very similar just without the last stage plugged in...

Alan

Froggy shark

Once more, thanks for your help, Alan

One of our fellow 928er is a US 928 owner, fitted with a third brake light from factory. May be he's gonna give me some help about it...

Next step is the DMM

Thanks!

Michel
http://monsite.wanadoo.fr/culte928

Hilton

Resurrecting this old thread..

I'm in the process of wiring in a third brake light on an '87 S4 (ex-UK car - they didn't get third brake light until 1990).

I'd figured out that pin 7 was the brake positive - however I'm getting no voltage.

Does anyone know if I need to change anything on the bulb control module?

Gonna go check the fuses now to make sure I didn't blow something taking off the interior light, but figured someone might have done this before

Froggy shark

Hi Hilton!

I gave it up for now, no positive on pin #7 neither, non matching colours on the spare loom that runs down the passenger (LHD) B-Pillar.

Scared me when I found that both wires from this loom were positive, but no link with the brakes (would be too easy).

Oh well, I would live without it a few months now

Cheers,

Michel

Hilton

Thanks Michel

I have a fallback - my '89 was fitted with the Hella 928 third brake-light kit when it lived in New Zealand.

I'll take the ceiling panel off and see where they wired it from according to Hella's instructions. I'll post back here with results.

Hilton.

sendarius

Guys,

Hilton has (kind of) alluded to my issue.
My '89 doesn't have the third brake light (yet), but the '88 does - however, the bulb control module connector has had the "brake light fail" pin removed. When I connect it, the dash has a permanent error light.

Is there a different version of bulb control module, or a known modification required to accommodate the additional current draw of the third brake light?

Alan

Yes there is... get the right vintage version...

Alan

sendarius

Would that be:
928 641 603 10 - Lamp bulb control module 87-95?

Hilton

Hi Steve,

I haven't had a chance to pull that rear cover on the hatch to check wiring - but I'm pretty sure my '89 has the same problem as your 88 and that the PO disabled the pin on the bulb controller (I didn't get a warning last time a brake light was out).

Will update later today - I got sidetracked by treating my leather interior with neatsfoot oil, and cleaning all the carpets with a carpet cleaner while it was in pieces.

sendarius

Thanks Hilton.

The '88 (as expected) does not report brake light failures.

The '89 DOES (and the warning light illuminates until I tap the brakes, as expected), but doesn't have the third brake light.

I'd like to get them both working properly, even if I have to resort to a soldering iron and modify the control module.