94 R129 300 SL 24 Electrical Problems

[James1976]

Hello all!

One of my first posts so please go easy! Come over to the light side from the dark side of a new BMW where I was a regular poster.

Right, just bought the above car. Whilst generally in very good condition the wiring's been bodged and is starting to do odd things. It's not the wiring loom though I don't think as from my understanding the 300 24's don't have the problem.

In the rear of the car, there's a wire running from one side of the feed for the rear lights to keep the other rear light on. With me? Please keep reading...!

I have a garage investigating at the moment. The odd bit is this - I can see why the feed may have been bodged in to cover up for a broken wire and provide power. When turning the lights on the warning light comes on in the dash thereby illustrating the bodge - however, all lights work fine.

This weekend however the warning light went out when the lights were on - result I thought - no bloody luck on that front it turns out later.

The fog lights (front and rear) will come on when the engine's turned off, but when the engine's running, they won't come on.

Odd or what? Leads me to think the lighting control box (if there is such a thing) is playing up, not putting out the right outputs at first and then the wrong outputs as it starts to deteriorate further.

Any thoughts or ideas from someone much more knowledgeable than me?

Thanks in advance all!

James

 

[James1976]

Diagnosis - the relay for the lighting has gone if anyone wants to know! J

 

[kth286]

Thanks.

Always good to have the feedback.

 

[Sp!ke]

Bridging left and right tail lamps might be something as simple as the fuses or the fuse box itself as left and right side tail lamps are on separate fuses. It could be that the retainer is simply dirty and the previous owner bodged it to get around the problem.

This bridge could be causing all manner of problems depending on how it was done so I'd start by disconnecting this wire and troubleshooting the tail lamp issue and work from there.

Other problems sound like they could be earth related. Personally I'd be spending a while armed with a decent multimeter tracing back the loom looking at all connections and earth points.

By the sounds of it, I would also pay special attention to the connectors inside the back of the ignition switch itself. A horribly fiddly arrangement so possibly best left to an automotive electrical specialist that one though.

 

[MD5]

A common problem on 124s is where the wiring feeds through to the rear via the bootlid hinge(s). I don't know if the early 129s have the same layout, but after years of the bootlid being opened and closed, the wiring loom passing through the hinged area wears out due to the bending back and forth. If the repair isn't carried out correctly (ie worn cable replaced), and the rear lights are simply bridged, you will have bare wires making contact in the hinged area. You will also have the warning light staying on, despite the lights appearing to work properly, plus possibly a variety of other problems, eg the boot interior light staying on or dimming etc.

 

[James1976]

Sp!ke, MD5, many thanks for your responses. I've managed to avoid a multimeter since school days although I'm having a distinct feeling I'm going to have to learn again. This is why I used to run a simple W123 before some sods nicked it!

The mechanic (a good, well known Fulham bloke) has diagnosed that the feed to the rear lights is intact and working OK but there's no feed out from the lighting relay to make it light. To be fair I have a phobia of this kind of thing (good with clanking metal bodywork and detailing but there it ends...) and just want someone to fix it. However, if the lighting relay box doesn't work then I may be down to learning again and weekends in the basements messing around.

Part's ordered from Germany so let's wait and see if it all starts working again when the new relay's fitted. Otherwise ABC of wiring and local automotive electrical techincians here I come! Watch for smoke signals over Borough....!

 

[MD5]

Good luck James!