Bizman928

My New Black Euro 1988 928 S4 has the annoying scenario that my headlights come up when I switch my sidelights on. They don't come on in anyway, just rise up & sit there ready for you to switch the headlights on?


How can I stop this or re-wire it somehow?

Thanks in advance.

Steve

MY89 928 S4 Stone Grey Metallic....gone but not forgotten......

My New 928 :-
MY88 928 S4 Auto - Black Analogue Dash .....- Back in 928 S4 ownership!

Alan

It shouldn't do this - so you need to fix whatever is broken...

Euros are not supposed to be different to USA models in this respect. Seems a likely culprit is the headlight switch - I'd start there - see if you can swap in an alternate and see if that solves the problem...

The pods should only rotate up when the headlight relay 86M terminal is active (~12V) - this should only be with the headlight switch in position II (of 0/I/II). The pods should only rotate down when the headlight relay 30b terminal is active (~12V) - this should only be with the headlight switch in position 0 (of 0/I/II).

You can test the switch operation at the relay socket (relay removed). If the switchgear seems OK - I'd suspect the relay next.

This simplified diagram may help you understand it better...

Alan

Hilton

Actually Alan, this is common behaviour for UK cars from 87-89 (and only UK cars). There was a bit of legislation introduced by the UK govt which remained in effect from 87 to 89 (I think possibly 1/1/1989) that required the headlights to come on dimly with the driving lights.

Its known as the "dim dip option" on the UK list.

There's a coding plug for the headlights, Its a 3-pin plug with a loop joining two of the pins, and IIRC, changing which pins are bridged will affect this behaviour. There's also a specific headlight relay for Great British cars (928 618 107 01) for this, from 87-89, along with a separate voltage regulator which provides the low voltage current in switch position 1.

I'll do a quick search and see if I can find the info I have stashed away - if I have to I'll just go and compare coding plugs in two of my cars which have the "feature", as one has the correct headlight position, and the other the headlights come on dimly but stay down (which I actually rather like - anything to increase visibility during daylight is nice).

Steve - the fact that the lights don't come on is probably a result of a normal headlight relay being plugged in, rather than the UK-specific one.

edit: I can't find the info on my PC - will have to go take pics later on of the two cars with different configurations. I"ll post pics tonight.

edit2: minor correction to "UK". It apparently also appears on Hong Kong cars, as that was a British protectorate in those years, and hence fell under the same legislation.

Hilton

Update - checked my thread subscriptions folder here, and found this thread with posts by Wally and John Speake on how to jump the coding connector T5:

https://rennlist.com/forums/928-foru...t-problem.html

I'll go take pics later anyway - as this has cropped up a few times and pics would help people.

Bizman928

Hi Hilton
Thanks for all the help here. Seems you have a good understanding of the situation. I Like the idea of the headlights on "dim-dip" whilst yjey are still down sounds a novel concept. Wonder if I can duplicate that?

Seems from the thread you posted, that John Speake gave the scenario for controlling and fixing this situation. Just need to have a good idea which module I am supposed to be playing with back behind the ECU's?

If you can post a photo that would make everything a lot clearer.

Many Thanks for your help with this.

Cheers
Steve

Alan

Well thats interesting. Yes UK cars have a few wierd things (alternate alarms too). I didn't pay attendtion to the posters location initially - in general most ROW cars are the same as US for this.

The diagrams do show a coding plug for UK - it swaps the connection that feeds the 86M connector from the Light switch II (Normal) to light switch I (UK). The coding plug appears to be down by the CE panel. UK links pins 3 & 2 all others link pins 1 & 2. I assume from the wiring that the dimmer unit is there also - but it doesn't seem to note it specifically.

The dimmer is driven by the light switch connector only when in lighting switch I mode - it should work regardless of the coding plug (does this low illumination mode work now?)

Alan

blown 87

Is that what the little bulb is for in the Euro lens?

Alan

No - this drives the headlamp bulbs on reduced power. While the H4 lenses have provision for an additional small bulb - I don't think any 928's ever equiupped this. Seems it was designed like this so you could combine side/parking/running lights into the headlights for some applications.

BTW to the OP - you can also simply unplug the dim-dip unit if you want to defeature the lighting part also.

Alan

Bizman928

Hi Alan & Greg

As Alan has pointed out, I have never seen another bulb in the main headlight

Steve

blown 87

Paul Hunt has a extra bulb in his OB, this is the only one I have ever seen.

Bizman928

Does he have a photo.....interesting idea. Wold love to see how it looks and the wiring.

Steve
New Black MY88 928

Hilton

Hi - sorry for the delay, I've been wrestling a PC failure in between 928 stuff and kids

Here's the pics of the dimdip unit, and the coding plug.

Its the silver box attached to the ECU frame on my '87, and is probably in the same place on an 88? The coding plug is separate from the dim-dip unit, so you can unplug the low-voltage module and set the coding plug to be "normal", and have the car work like the rest of the world (i.e. driving lights, and headlights down in position I).

The coding plug shown is set for dim-dip.

Or you can fiddle around and have it like my '89, with dim lights on, and headlights down, in position I

Bizman928

Thats great Hilton
Thanks for the description and photo's. I cannot seem to find my "dim-dip" module so guess the last owner may have removed it. Might be why my Headlights don't come on in dip mode.

Like the thought of having my headlights come on in dip mode whilst they are down.....have you got a photo of how this looks on your 89?

Enjoy the weekend and thanks again.

Steve

New Black MY88 928 S4 Auto starting its transformation and new life

Mrmerlin

Hilton this is good info, can you please explain what exactly has to be done ,
IE what wire to move or system to have connected,
Thanks again for the pictures, Stan

blown 87

I do not know, I know he has a camera as I have seen him use it, I just never have seen a picture he took posted.