I have a 2004 Vanden Plas with 155,000 miles on it, 4.2L V8. From time to time in auto headlight mode the headlights will flicker on and off during daylight. In non-auto mode if I have the headlights turned on at night I also get the flicker sometimes. I had an electrical mechanic check the wiring; he found everything okay from headlights back to dash, but couldn't go any farther (non-Jag shop).

I suspect the dimmer switch itself. Sometimes though when I apply the brakes the symptoms will occur, which leads me to think it may be a wiring problem somewhere. Or maybe the sensor is bad or dirty--is that located on the backside of the rearview mirror?

At any rate, I'm thinking of replacing the dimmer switch since I can get one for a little over $100, and having my Jag dealer take on the problem could get pretty expensive.

Any ideas on the issue and, if I replace the dimmer switch, any advice on how to take the steering column apart in order to get to it? It appears to be a plug and play part, so I expect getting to it will the most difficult part of the job. Thanks!

 

Not sure I understand what the dimmer switch has to do with the headlights flickering, as the dimmer switch regulates interior lights.

Do both headlights flicker at the same time, or are they flickering independently of one another?

If they are flickering independently, it sounds to me like your headlight bulbs are dying. I had to replace the bulbs in my 04 VDP about a year ago when one started flickering, which soon progressed to flickering and then turning off. If you do need to replace the bulbs, replace them as a pair.

If both are flickering at the same time, then it sounds like a relay, switch or wiring problem upstream of the headlights. It doesn't sound like the light sensor, as you say the problem also occurs when not in auto mode. And even if it occurred in auto mode, auto mode uses a Schmidt like trigger (delay) to prevent the lights from going on/off every second or two in marginal light conditions.

 

Thanks for your answer. By dimmer switch I mean the lever on the steering column that controls high beam/low beam (dimmer), along with turn signal, etc.

I did replace both headlights a couple months ago with this issue; the headlights needed to be replaced, but that issue is apparently independent of this issue. I'm not sure if the lights flicker at the same time--that's a good troubleshooting distinction to make, and I'll monitor that. That's also helpful to know about the delay mechanism in auto mode.

 

Also ... check the headlights' earthing points (on the car's frame); they seem fairly notorious for causing all sorts of problems on this model.

 

Where would the earthing points be--just follow the wires to where they are grounded on the frame?

 

So after doing some searching back through old threads on this forum it seems the flickering headlights is a common issue that is most often related to the turn signal switch arm attached to the steering column. So I'm going to replace that and see whether it fixes my problem.

 

I went ahead and bought another turn signal/dimmer switch. Standard Motor Products makes an aftermarket switch, but they themselves are actually out of stock on this item with no indication of when they'll be available again. So I ended up spending about $100 more for a genuine Jag switch. The best deal I found was at AutoPartsWAY.com for about $15 less than anywhere else with "free" shipping.

I installed it this morning. It wasn't difficult at all to take off the bottom and top cowls in order to swap the switch. The most confusing part was removing the two screws on the bottom cowl. They're just philips head screws, but I couldn't tell that they were actually turning until I was willing to wrench every part of my body to practically screw myself under the steering column to see what I was doing.

Everything works, but a few road trips will expose whether the flickering is still there--I expect not. I'll post again whether the fix resolved the issue.

 

A new column switch cured my identical problem entirely.

Of course they are not cheap. When I examined the old switch it was obvious that Charlie Allthumbs had fiddled with it, as one of the top securing tangs was snapped off. Clearly the fault had been left for me to find !!

 

That's nice to know the same fix took care of the problem on someone else's vehicle.

 

Issue seems to be fixed. I'm grateful for that.