Hi all, finally got my car back after having had the alternator replaced and it's driving like a dream.

The only problem is that my dipped beam headlights are not working. I plugged my code reader in and it said short to ground, but I've erased the codes and checked the earth points behind the headlight are good.

fuses are good, and I've put 2x brand new bulbs in.

I can only now drive the car in the daylight 😑

 

If yours is equipped with HID lights, it sounds like a headlight ballast has gone bad. The ballasts are mounted to the bottom of each headlight assembly, so you'd need to pull the bumper cover to get that headlight out. When bringing my XJ back from the near-dead after I purchased it, that was one of the many broken things I needed to address straightaway.

Good luck!
Paul

 

Could it be the lighting switch on the steering wheel binnacle ? These are notorious failure items, and caused me once to lose ALL lights approaching a sharp bend on a minor road on a moonless night a few years ago.

 

If both dip lights are out, then it is not a fuse as each light is separately fused.
If you suspect a HID is problematic causing an overload, perhaps by removing each fuse 8 and 9 separately to see if you can get one light working. That will help you eliminate a single assembly.

Could be integrated relay 11a in front power distribution fuse box failing.
Check front power distribution fuse box plug EC40 pin 8 (blue wire) to see if it has 12 volts when lights are off, and then if it is effectively going to zero (being grounded by front electronics module) when light switch turned on.
If so, then relay R11a should be getting activated. Then check if you are getting 12 volts through fuses 8 and 9 (to dip lights left and right).
If relay is on but no 12 volt output to fuses 8 and 9, then you likely have bad/intermittent contacts in R11a (not a user replaceable relay as soldered directly into the PCBs of the front power distribution box).

If however the plug EC40 pin 8 (blue wire) is not being grounded (going low), then the front electronic module is not sending the light request through to R11a.

If you want to meter out the headlight switch integrity, then it has internal series resistors incorporated to send the correct command to the instrument cluster that then communicates through serial communication to the front electronics module.
The light switch assembly has plug IP 26 connecting to it.
IP26 Pin 6 is the ground return (Black/white wire), so any of the following resistance measurements should be taken back to this point.

IP26 Pin 4 (White/Red) is the variable resistance output to the instrument cluster.
Switch in off position = 56 ohms.
Switch in side light position = 236 ohms.
Switch in dip position = 506 ohms
Switch in Auto light position = 976 ohms.

As a comparison, the exit delay switch output on the stalk follows the same resistance steps and is on IP26 pin 3 (White/green)
Switch in exit 3 position = 56 ohms.
Switch in exit 2 position = 236 ohms.
Switch in exit 1 position = 506 ohms
Switch in Auto light position = 976 ohms.

Hope this helps you troubleshoot if you haven't found a HID assembly faulty.

 

I had one side not working even after changing that bulb,
went ahead ordered 2 ballast Lad5g from valeo oem 12 pin for my 2003 took of the bumper , unscrewd both headlights to change the ballast wich is hidden underneath each headlight.
later models only have 4 pin ballast


you can also unplug the headlights from the top under neath the tray ,might want to have a look at those connectors

 

Thanks for the excellent detailed information. I expected a fault warning to show up on the dash but nothing shows. Is that to be expected?

I am waiting for a dry day to go through your check list so fingers crossed.

 

what if EC40 pin 8 (blue wire) isnt live at all with the lights off or on could be the problem ?

 

hi, i have normal bulbs in my car , the fuses are not live in the engine bay fuse box. Number 10 and 13 , 20 amps.

 

Hi 389stone,

Ok understood, you have Halogen inserts, not HID.
What year of production is your car?
Production changed around 2004, so there are several different schematics depending on your car's year which can mean major differences in what services run out of which fuse box, fuse numbers and wire colours.