96 3.8L Firebird Electrical Weirdness

Hi Guys, hoping someone can shed some light on this. Jumped in car turned Key and all the electrics went dead. Dash lights came on very dim and car would not turn. got it jumped started and figured the battery was dead. Headed off to battery shop, noticed that none of the lights were working. Parked up and went to put main headlamps on and the engine cut. Same thing, electrics dead. Put new battery in and started no probs. Disconnected battery and engine cut. New alternator put on, engine runs even when battery disconnected, but as soon as i switch on headlamps. Engine cuts. Do headlamps run direct from battery or something? any ideas?

Yes, the headlamps get juice directly from the battery. Check all the wiring to the lamps as well as grounds. Good luck

John