I've seen other threads here relating to absent daytime instrument lighting (making it difficult to see the physical dials on dull days) - where the fix has been to select the headlamp switch to OFF and then use the dimmer control to turn them back up.

Well this hasn't worked for me (XK 4.2, 2007 owned for 14 years), and I'm completely baffled because here's the full story:-

The speedo and tacho dials have always previously been illuminated during the day, but suddenly weren't with no obvious cause. The small information screen between the dials continues to light up normally day and night. Switching the sidelights or headlights on (either AUTO or manually) activates the instrument lights correctly, and when on, the dimmer switch correctly adjusts their brightness, including the satnav and information screens and all the switch illumination. The brightness of the instrument lighting at night is undiminished from previously with complete coverage. Sat in the car at night with the engine running and the headlight switch ON or AUTO (so everything is lit up fine), when I switch the headlamps OFF the instrument lighting fades out slowly to complete darkness while the switch illumination goes off immediately. Previously of course the instrument lighting wouldn't have gone off at all when the engine is running.

I don't think it can be dead LEDs in the instrument cluster because it's all fine at night, nor a faulty dimmer because that works perfectly at night, nor a dodgy ribbon cable because the small information screen works perfectly, nor a fuse, nor the battery (relatively new and fully charged by CTEK) ... so any ideas?

Thanks

 

Possibly a hard reset may fix it to reset a module somewhere

 

Thanks for that suggestion.

I'm borrowing an iSoft/Jaguar scanner today to check for any fault codes and if nothing found will try the hard reset.

I'm aware I'll need to reset the windows afterwards, but a bit concerned that others have mentioned things like electronic handbrake, seat memory, configuration/calibration settings etc. being lost?

 

All of that is very easy to do and will take 5 mins at most

 

And I don’t have these concerns. I reset my car every spring without issue.

 

Hi, Well there were no relevant or major fault codes showing on the iCarSoft scanner, the minor ones all cleared and didn't come back, and the instrument lighting issue remained - so no clues there!

So I did the hard reset, which as expected lost the window positions, trip readings etc., and as you said Woosie wasn't a big job. Unfortunately the instrument lighting issue still remained.

Some more tests confirmed all the functions of the dimmer knob, light level sensor, brightness preferences on the satnav screen, side/headlight switches, AUTO lighting etc. are working properly - so nothing I can pin down as the cause.

Obviously this isn't a big problem, because manually selecting sidelights on dull days brings the instrument lighting on (and as 2007 XKs don't have daytime running lights that's probably a good idea anyway!), but that loses the AUTO convenience and makes loads of warning bongs when you forget to turn them off.

Any other suggestions?

 

Don't feel bad x150cambs. You're not alone. My '09 XK has the same issue and does the same as you've described. I've tried all the "fixes" suggested here, and nothing seems to make it better. Granted it's a relatively small matter, but like you, I wish the center cluster was readable all the time, especially in daylight.
Welcome to the board.
Cheers.

 

Thanks for your support David993S. This sounds like it might be a common problem then .... but hopefully someone somewhere has been nerdy enough to keep going until they found a cure!