Lights please!

[bulk66]

Hi all had my new 89 mk2 8v Gti a week now and got a annoying problem my dash dose not illuminate when I turn on the lights instead its as if the dash resets its self turn the lights off and alls good again, I've tried another switch that I know works fine and it dose the same thing I know the light dimmer can cause problems on these I did notice on turning the illuminater wheel thing that the oil pressure warning bulb brightens and the rev counter moves up n down slightly. The head lights, main beam, break and number plate lights all work fine when the dash throws a wobbler.

[bulk66]

Bump 

[KRdubber]

Does it happen every time you turn the lights on?
If when operating the dimmer switch the oil light illuminates and the rev counter goes up n down the only two things I can think of off the top of my head is either the printed circuit on the back of your instrument cluster or of course chafed wiring or a bad earth?

[bulk66]

I've tryed another switch and the rev counter dose not drop but I still have no illumination on the dash, the indicator light, temp light etc also work? It's driving me mad 

[KRdubber]

Am I right in thinking that now you replaced the dimmer switch your instrument operations except for the illumination are working as intended?
If so have you checked the bulbs for the illumination?

[bulk66]

That's my next job now mate replace the bulbs 

[bulk66]

 Right I've still not sorted this, I've just put a new speedo in it and it is still not lighting up any body got any more ideas 

[bulk66]

So just to go over things again, I tryed another light switch this didn't work, new speedo, all the LEDs in the middle of the dash work ie indicators and the rear number plate lights work so not fuse. It dose have a after market CD player that seems to be permanently on as in you can have it playing when the keys arnt in the ignition any body got any more ideas.

Also if I turn on the lights and put on main beam the digi clock / MFA computer goes off, rev counter drops a bit and the temp lights flashes for a while   

If the fog light switch is bust would that cause any issues with the dash lights?

[dj_adam]

You could try systematically removing each switch individually and testing the dash each time. Try with the stereo removed also. Sounds like there could be a short somewhere. The blue/grey wire is connected to everything that lights up on the dash, if its connected incorrectly to one item, it will affect all switches/clocks etc. Start with the stereo and disconnect the blue/grey wire and go from there. If you have a multimeter you could also check the wire for a +12v when the light switch is switched on.