Not sure what's going on, if it's a ground cable or the alternator is playing up ?
Basically when my glt starts up from cold the headlights come on very dimly even though I haven't turned them on.once the car is warmed up they're off. Also my pre amped sub crackles when the car is running but fine when the ignition is off.

I'm stumped, I'm not sure if something has shaken loose, anyone had similar experience ?

Try sniffing around the three connectors onto the back of the fuse box. Something like here: viewtopic.php?f=57&t=9808

cheers for that info, gonna check it out at the weekend and hopefully it's something similar.