Technical Banger 6 to 12 volt

Put a 12 volt neg. ground bat. in all works good but put on the brakes and the head lights go dim ? Whats up with that ??

 

Are you saying you installed a 12 volt battery, into a 6 volt system, without doing the 6 volt to 12 volt electrical conversion ?

 

did the conversion and new alternator the works , not running turn lights on hit the brake and head lights go dim ?

 

I would check the grounds for the headlights. If grounds are bad, the headlights will try and ground thru some other path. Do the tail lights dim when the brakes are actuated? That might help pinpoint the problem.