I have an el fairmont ghia. When i put my park lights on the instrument lights come on a little then fade quickly to almost nothing. The lights on the radio are out compleatly when park lights are turned on could this be the problem. Recently changed clock and instrument lights to blue leds but they were all working fine. I did have my headlights out to make them more clear, after putting back in the problem was there. Have checked all fuses and all is ok. Also the brightness control and seemed to only make the crystal display change. Is there a seperate rister/regulator for the instrument lights. Can someone help or point me in a direction as it has me stumped.
I did have the power stering pump out as a seal went so it has been replaced. i don't think it is the alternator as all other nights seem to be good and bright.

Any help would be mostly appreciated. Thanks guys.

check the wires too see if there are any faulty ones, also check the output voltage on the battery whilst the cars running/underload etc..

Try holding the brightness control on for a while. Mine takes quite a few seconds before it starts to effect the dash lights.

Is the dimmer switch on dim or bright?

Its not a 2 position switch like lower model Falcons. Its a dimmer switch. Can vary the brightness from hardly see it to OMG I need sunglasses.

Ahhh k then I stnad corrected.

yeah i have tried the dimmer switch holding it up. The clock and the climate control and odomator dim and get brighter but nothing else. I replaced the alternator a few weeks back. headlights seem really bright as the rest of the lights. will check the batery voltage tho. About to go pull it appart see if i can see somthing.

All good problem fixed. Turned out to be a short with one of the leds i put in. Tho ant sure why it didn't blow the fuse. Thanks for the help guys.