Heres a doozy for all. After rebuilding my GTS and putting it all back together i started it and all is well. Now for some reason i cannot use my light switch to regulate the brightness of the gauge lights or interior lights. This only happens when the ignition is on the on position and the either the park lights or normal lights are on. All gauges work fine and as soon as i increase the brightness for the guage lights using the light switch, the TEMP and FUEL gauges go past the EMPTY and LOW position. The gauge lights do not work, however the heater control lights work fine. The interior lights work fine when i open the doors. I have replaced the light switch with 2 NOS ones and the same thing happens. I removed the 3amp fuse for the illum lights and all is fine when i turn the light switch to increase the guage light brightness (obviously not going to work, no fuse no power).
Now when i had the car running the other day i did smell something like plastic burning, but i was unable to determine where it was coming from and throught nothing of it until now. When i checked my wiring i had the red wire that runs directly from the ALT connected to BATT side of the AMM guage. I moved this to the GEN side of the AMM gauge and it seems to be operating okay, although a little funny.
Sorry about the long message and i hope someone can point me in the right direction.

Thanks Zappa. Ill double check again. I dont think the HT GTS had a head light relay. I cant see it in the wiring diagram and also in the engine bay.

Was thinking about your dash lights today.
I will almost bet the switches earth is dirty. I think this because you have fitted other switches and have the same probelm.
Have a look where the switch is mounted through the steel dash.
This area should ha

Zappa, your right the dimmer lights wont work until the switch is properly earthed. I think i know where the problem lies. Ill check tonight. I just dont wont to take the dash out if i dont have to. Its newely chromed and painted and dont want to scratch

Zappa, just to let you know i fixed the problem. Turns out to be a faulty earth wire. I still dont know where (earth wire is definitely connected). So i made up another and earthed it. Now its perfect.