S4 Lighting relay where is it ???

[LVC]

Bonjour all - long time no speak (2017 my last login ..... shame on me)...

Anyway the S4 is still alive and kicking up dust on the French roads near Le Mans ....

I need your help ..... headlights/rear lights don't work ...

Parking light front and rear does, passing beam/flash does but dipped and side lights and rear lights don't.

Fuses are good (unless some bugger has hidden a special one somewhere I haven't found) so am thinking "relay" which is a micro-switch .... so before I take the handlebar switch apart can anyone please tell me where the chuffing relay is for the lights on a 2001 S4..... There's three obvious ones by the air filter and swapping them around hasn't changed anything so I'l guessing it's somewhere else ????

Thanks in advance

Photo of the beast for those that remember me ^^

[Darren69]

Iirc there isnt a lighting relay so your problem may well be a faulty switch.

[LVC]

Originally Posted by Darren69

Iirc there isnt a lighting relay so your problem may well be a faulty switch.

Thanks.

I've just taken and rebuilt the switch (need about 10 hands with 20 fingers on each) to get it all back in and all good .... there's no "positive" getting to the lighting part of the switch so currently into the Workshop manual trying to figure out where it gets its power from.

Yes no relay on this model from what I can see (the ST4 has though annoyingly).

Will keep looking

[Flip]

Sounds right if it switches the ground.

So when you say ‘parking lights’ work do you mean when the key is turned to ‘park’ after the steering lock position?

Do you get the position/side light on with a tail light with light switch in the on position with the ignition on?

Ok so no dip beam but does the head light come on with the ignition on and switch set to high beam (not the pass/flasher) or is it the complete head/tail light circuit out?

[LVC]

Originally Posted by Flip

Sounds right if it switches the ground.

So when you say ‘parking lights’ work do you mean when the key is turned to ‘park’ after the steering lock position?

Do you get the position/side light on with a tail light with light switch in the on position with the ignition on?

Ok so no dip beam but does the head light come on with the ignition on and switch set to high beam (not the pass/flasher) or is it the complete head/tail light circuit out?

Hiya, Yes turn the key beyound steering lock to park and the front and rear "sidelights" come on as does the dash.

I get nothing at all, neither front nor rear, side lights or dipped beam when the switch is activated and ignition is on. So complete head/tail light circuit is indeed out.

High beam only works as the pass/flash and blue main beam comes on on the dash cluster.

Brake lights front and rear work also so does indicators and in fact everything else just no lights

[Flip]

Okay apologies for this question - we can pin this one down but do you have a multimeter?

My feeling is the handlebar switch is giving the issue as you have nothing working from it. You have side and tail light from the park position- which circuit is switched by the the ignition barrel.

So you need a meter to check if there is continuity from the switch to the corresponding pins in the connector from it.

On my 900 they are in a ‘superseal’ connector fixed to the headlight bracket but I am not so familiar with an S4 to know exactly where to find it I’m afraid, so you may have to play ‘follow the wires’ from the switch until you track it down.

[Dukedesmo]

Obviously if the switch is faulty you will need to repair/replace if first but if you then modify the wiring to add a relay (switching through heavier duty wiring), you will get a brighter and quicker-on headlight whilst reducing the chances of overloading the switch again.

[LVC]

Yes indeed - will go check the switch wiring (all looked good when I had it apart) and report back

[LVC]

Checking complete - switch is functioning correctly (checked side/dipped light switch also Engine cutoff /big red switch and starter button and all good).... off to follow some wires now

Checked with a multi-meter and all circuits on the handlebar switch showed working (shows 1 when open and 0 when closed/operating) correctly.

[Darkness]

Do the handlebar switch cables have a block connector behind the headlight on the S4? Worth checking, as is the state of the wiring around the headstock.

[LVC]

Originally Posted by Darkness

Do the handlebar switch cables have a block connector behind the headlight on the S4? Worth checking, as is the state of the wiring around the headstock.

Yes they do and am checking that ATM along with the continuity on the rest of the wires

[LVC]

Well what a chuffing PITA that was ....

Good old Ducati had changed the wiring between my 2001 S4 and the Workshop manual I have for the 2002 S4 ..... and what had they changed ..... they have removed the stupidly, stupid capacitor/diode/piece of crap thingy that is hidden in the wiring loom on the side light circuit from the switch.

By pure luck I cut into the "bulky part" of the loom just behind the head stock to find than either side of a well hidden "lump" on the side light circuit I was getting no continuity ..... offending item bypassed as a test and all works ..... so now has been permanently removed and the two ends of the wire correctly connected and all is good again ..... you have got to love 18 year old dodgy italien electrics

For those interested here is the chuffing part that is dead and causing all the problems ....









Thanks all for your help - we got there in the end

[350TSS]

what was the purpose of the diode in the original design, does anyone know?

[Darren69]

I'm not sure of its function in this instance but it doesn't look like a factory fitted part to me, it looks a bit home brewed tbh.

[LVC]

Originally Posted by 350TSS

what was the purpose of the diode in the original design, does anyone know?

Originally Posted by Darren69

I'm not sure of its function in this instance but it doesn't look like a factory fitted part to me, it looks a bit home brewed tbh.

I wondered that but as the only 1 other previous owner definitely didn't add it (he was just about capable of adding petrol) it's a bit strange where it can from - there's a bunch of other "connections" in the same place but just look like a standard branching of a wiring loom - don't seem to be any other diode/thingies anyway.

I'll add it to the list of other "weird" stuff that this bike has got - sure it was a prototype for bad ideas