WHAT IS THAT BLACK RELAY LOOKING THING WITH THE BIG PURPLE WIRE GOING INTO IT.RIGHT BETWEEN THE FUSE BLOCK AND THE DIMMER SWITCH.IT IS A 74 CUTLASS SUPREME (442).THE REMOVEABLE PART IS NUMBERED ON EACH OF THE FOUR PRONGS?????????

 

NVWindow, on older cars like mine, purple is usually for primary (12 volts), or sometimes pink. If it goas to your dimmer switch, I would guess it is your unswitched 12 volts but I am not sure. If you say big meaning larger guage than the others this would lead me to think that even more so. Can you get a voltmeter to check that? Or do you have a friend that can help you? That would be best. What is your trouble?

supreme3.4dohc, what kind of question do you have about the alternator?