Ever try driving at night with the instrument lights full blast bright?

My 2005 XJ8-L, has that unique feature. Was during the last year a once every now and then problem. Sometimes would fail full bright, other times almost off, but this time "KAPUT" failed at full bright and has not changed.

How does the unit with the dimmer in it come out and once out, can the dimmer alone be replaced? Full bright at night is the real pits.

Any help is appreciated.

Garfield

Submitted by vineyardman68@… on Thu, 10/24/2013 - 15:46

Steve, thanks for the reply.

Ok. Cars in the garage, so it's dark enough.

First test: No key in igination> Turned lights on with the switch on the turn signal. Lights in main instrument cluster--Bright,-- but other lights on dash- clock, Steering wheel and back lighting of center console-- would dim and brighten with dimmer switch.

Second Test: Key in igination, key turned to position two> Turn signal switch in AUTO position--same thing--main cluster bright, rest of lights up or down with dimmer switch----BUT, then main cluster began working with dimmer. So all lights went up and down with dimmer.

Third test: No key in igination: Turned light on with directional switch. Main cluster bright, the rest worked with dimmer.but.then after about 15 sec. all returned to bright and would not respond to dimmer.

Fourth Test: Key in ignination, key turned to position two: All lights bright, would not respond to dimmer.

End of Test.

Are there any other test I can do?

Garfield

Submitted by vineyardman68@… on Thu, 10/24/2013 - 15:20

Edited on 2013-10-24 23:00:03
Steve, thanks for the reply.

Ok. Cars in the garage, so it's dark enough.

First test: With key in igination-not turned> Turned lights on with the switch on the turn signal. Lights in main instrument cluster--Bright,-- but other lights on dash- clock, Steering wheel and back lighting of center console-- would dim and brighten with dimmer switch.

Second Test: Key in igination, key turned to position two> Turn signal switch in AUTO position--same thing--main cluster bright, rest of lights up or down with dimmer switch----BUT, then main cluster began working with dimmer. So all lights went up and down with dimmer.

Third test: With key in igination--not turned: Turned light on with directional switch. Main cluster bright, the rest worked with dimmer.but.then after about 15 sec. all returned to bright and would not respond to dimmer.

Fourth Test: Key in ignination, key turned to position two: All lights bright, would not respond to dimmer.

End of Test.

Are there any other test I can do?

Garfield

(Follow up:)

Driving tonight. Started out with all lights controlled by dimmer, were on full bright.
After about 10 minutes, lights started working with dimmer.
After about 5 minutes, lights went back to full bright. Rest of 30 minute drive, lights remained full bright.
I guess the conversation with the two elements mentioned, just gave up.......

Submitted by stevejag@sbcgl… on Thu, 10/24/2013 - 12:11

Edited on 2013-10-24 12:12:45
Let the education begin!

Most people don't realize it, but the interior lighting system in ANY modern car is one of the most complex systems in that car. It's just the nature of the beast, the system goes EVERYWHERE. And these days, the theater type dimming and fade away lighting has to be controlled by something.

In your case Garfield, that switch is only part of it, and we need to find out a few other things. The dimmer knob in that switch pack is connected to the Instrument Cluster itself, but it doesn't DIRECTLY control the level of the lights, it's just an input of the driver demand. From there the Instrument Cluster controls it's own lights based on that demand. Here's where it gets interesting. The Instruments then relay that demand to the Front Body Control Module Module which is the master of all the other interior lights. In essence, the IP sends a message over a network that says "Hey, the guy in the seat told me he wants the lighting at 60%", and it complies by making the lights 60% in brightness.

So, what we need to know Garfield, is what do all the other lights that are controlled at the same time do in response to the dimmer knob. When it's dark, turn your lights on and see what happens to all the switches on the dash, steering wheel and in the doors. Do those lights act like the Instruments and stay at full brightness, or do they raise and lower like they are supposed to??

If they respond correctly, you know the dimmer control is OK, and the IP is a suspect. If they act just like the Instrument lights, the first suspect is the dimmer control. Remember I said suspect. Further diagnosis to confirm will still be required, whether by you or your friendly dealer.

Good luck!