My problems never seem to end .... getting pretty sick of this car now ... ( unquestionably the most unreliable heap i've ever had )

current problem is that if i switch the lights on, even just to the sidelights, then the outside lights will come on as normal, but all the interior lights

-button lights
-door handle lights
-dash + needle lights
-console lights
-waterfall lights
-etc

will initially light up nice and bright then fade down to be totally dim / almost off.

If I then twiddle the dimmer, then they will initially go brighter when the dimmer goes up, but then fade back down to nothing ... eventually even this effect dies down till the lights do nothing when you twiddle the dimmer either way.

Odd thing is that all the outside lights work as normal.

The LCD message centres on the MID radio and the speedo also work normally all the time. they even go brighter and dimmer when the dimmer switch is moved up and down.

Any thoughts? Is it more likely to be the switch, or the light control module. V8 or else ...

have you had or done any programming, if not.. start by disconnecting the battery first and give it a reset.
if there is a fault as you said it can only be one of 2 things, i do have a spare light switch that you can try, that would eliminate that. V8 facelift Range Rover Autobiography 22" wheels.
1976 Harley Davidson Iron Head Sportster

Been having a think about it.

The only thing I can think of that relates to it is that I pulled the radio out a couple of weeks back to fix the pixels on it. In order to get to the radio, I unwittingly disconnected the main light switch as you need to pull off the side vents of the dash where the switch sits. When I did this, the car switched the lights on and popped the message headlight delay on the dash. ***

( yes, I know I should have disconnected the battery ... forgot ... was in a rush cause I did it in between showers of rain )

As soon as the switch connector was replaced, the lights went back off and message gone. Turned out it was a repeatable error ( I was curious ... so i disconnected it again ... ) I then disconnected the battery.

Anyhoo's after doing the radio, I put it back together and the same issue I described appeared then ... but it went away. I cant remember if I pulled the disconnected the battery or not to reset it. I dont remember any errors being logged on the car either when I checked it.


Will read the codes on the car and pull the battery tomorrow. Failing that, I may take you up on the switch. Although I have my doubts, as the switch dimmer dims the LCD's and the rest of the lights react to the dimmer upto a point, which would imply the problem is somewhere further down the line ( i.e. the LCM )

The behaviour almost reminds me of a capacitor in how it fades down ... its not instant, its almost like a little delay going up and down in brightness. Unfortunately, its not obviously clear on how the dimmer is used. The circuit diagrams I'm looking at dont clearly show where the dimming occurs. it shows the switch position circuit as inputs to the LCM, and also the output circuits to all the LED's etc ... but I cant seem to spot the dimmer part.


*** Will need to read up about that ... maybe that reaction is correct as the LCM thinks that its the same scenario as you would have for the headlight delay. i.e. ign off, then light switch off ( by disconnecting it ) = headlight delay. V8 or else ...

From something I found on the web ... just placing it here so I dont have to go looking for it:

Light functions
The light check control module controls and monitors
all external vehicle headlights and lamps both when switched on and switched off (cold and warm monitoring)
all switches and buttons for light functions The functions of the dimmer for the instrument lights and locator lights

Components
With the exception of the brake light switch, all switches scanned by the LCM are designed such that they
switch to ground. The following switches are scanned by the LCM:


Combined switch for parking light/low beam

Turn signal/dip switch

Fog light switch

Brake light switch

Hazard warning push-button

Dimmer potentiometer for instrument locator lights

The LCM receives further information via the I-bus/K-bus.

Light switch
When the light switch is in rest position, all contacts are closed (R <1> 1 MOhm) in the low beam or high beam position. The lighting for the light switch is controlled separately by the LCM. It lights at full brightness when the light switch is in the OFF position. It is dimmed to the same extent as the instrument and locator lights when they are switched on. V8 or else ...