all headlights intermittent

[jagfanken]

hi have taken car out at night during the days of freezing ice and on driving with headlights on suddenly they went off plunging road ahead into total darkness this was frightning touched lighting switch they came on then further down road went off again moved switch came on and stayed on till i got home didn,t go off when parked it has done this 2 to 3 times when driving in dark anyone got any ideas as it is dangerous ken

[PaulGover]

When I first bought my X350, second hand, there was a lighting issue down to a broken switch stalk on the steering column, so that's one possibility. The control uses a single wire (different resistances indicate different positions), so damage to that wire, e.g. short or break, would cause such symptoms. Then there's earthing - the headlights earth to a stud on the back of the front cross-member, and it has a history of corrosion issues which are sometimes "cured" by tightening. The trouble with that is the stud is only aluminium and snaps if you over-torque it. Then there's the headlamp relay to consider.

You didn't say which sort of headlights: HID or halogen. The former adds a whole lot of complexity to go wrong (about which I know nothing).

[JimMann]

If everything goes off, then that says there is a break in the circuit continuity, either at the earth point, or the power to the circuit. As the lights come back on instantly when the switch is "fiddled with", then that would seem the logical place to start fault-finding, looking for a dry joint or failing connection / wire.
Jim

[jagfanken]

hi many thanks for your replys i changed the switch unit months ago due to the trip button not working the unit i put in was a secondhand unit and although i tested lights etc every thing was working but only used car during the day but due to weather and it getting dark early have found this problem i can sit in car and lights seam ok i will check to see if i can find earth to the lights and i have another unit this was stated as working so can try this also can you advise to where the lights relay is many thanks will advise you of results may take a few days to check all these ken

[andypryce]

I would definitely suspect the earth point behind the headlights. Yes, it does tend to snap off if you tighten it, but that's a sign it's no good anyway. Just drill a new hole adjacent and reattach it. I can't remember where the relay sits, sorry, others will know I am sure.

[jagfanken]

many thanks for all replies i will look at all the points made and let you know how i get on may take a few days as so near to christmas but car is excellent other than this problem ken

[Alan C]

I would definitely suspect the earth point behind the headlights. Yes, it does tend to snap off if you tighten it, but that's a sign it's no good anyway. Just drill a new hole adjacent and reattach it. I can't remember where the relay sits, sorry, others will know I am sure.

I agree, easy to replace and easy to reach. I had the same issue.

[XJ_Driver]

Hi,

My first post here since buying an X350, having recently graduated from an X308...

It seems my 2003 3.5 SE has recently developed this same lighting fault - all lights fail intermittently. I cleaned up the headlamp earths last weekend (replacing one of them), but annoyingly the fault is still present. I've since noticed that if I touch the lighting control (LH) stalk the lights come back on again, so suspect the switch to be the culprit. But is replacing the switch a simple task, or is it not going to be that easy? My car has halogen headlamps.

Advice appreciated. Thank you.

[PaulGover]

I had that problem, and had it cured by the dealers with a new switch.

According to my workshop manual, basically remove the steering column lower cowl - this might need removing another panel in bottom of the instrument panel for access, but it's all simply screws, then remove the switch, again screws, and unplug the connector by squeezing the receptacle to get it out. Reassembly is the reverse, don't overtighten the screws - 3 Nm torque. Take care not to trap cables when you reassemble - doing so might have been the cause of this very problem!

It might, of course, just be a bad connector or similar, but most likely a damaged wire, so it might be repairable if you can work out where.

Make sure you get the right replacement part number - there are variations depending on what features your car has, such as automatic lighting. I don't think the HID lamps will affect it though, they should be the concern of some ECU somewhere - it's not like switches actually do anything these days, the just beg some ECU to change its mind

[XJ_Driver]

Thanks Paul - in that case I'll investigate the switch. I was only checking in case a new indicator / lighting stalk might need configuring to the car? Hopefully not then. Thanks again.

[PaulGover]

No, the stalk is just a collection of switches and a variable resistor. The click settings are just stops on said resistor, and the ECU reads the resistance to decide what to do. There's no processor in the stalk, so providing you replace like with like, all should be well. I suspect even like with unlike works, but you get confusing labelling.