i have a 91 firebird L03 and changed it over to a L05 and put headers and changed my intake and injectors. before i changed it over i had a problem occur everyonce in a while, i would get off work go ouut and start the car and it would fire right with no probs but but would look at volt guage and it would be at 10, i would then turn off headlights and fan and most of the time the guage would shoot up to about 14 and then turn headlights back on and fan back on with no more probs with guage going down. it came time for engine swap.I swaped out the 305 for the 350 and the motor had 4 heavy brackets up top by the intake some went down by exuast manifold, and so forth i changed over to headers and did not put these back on.when i started this car up again it run for about 5 mins and the guage would say about 10 volts so took alternator in to autozone(i know auto junk) and got another alternator, but still showing 10 volts so i took it back and went to test it but there machine was bad wasnt showing anything. put another alternator on there and still showing 10 volts. im not the greatest at being a mechanic but the only thing i left unplugged was oxy sensor, and the water temp sensor on pass side in the head. and i dont know what way to wire my starter back up ive got the chiltons book and i believe i got it back in the right order. but now it takes about 15 mins before draining the battery. need to figure out what is causing this to happen. if anyone can help please do. thanks if you can help.

 

could be your voltage guage is defective.

 

but it drains my battery in about 20 minutes. i take the battery out and put it in my grand prix just to charge it back up and the gp almost doesnt start.the only thing i diddnt hook back up was the AIR Pump all emission stuff is off.i got two ground wires on back of both heads connected and the main ground for the battery on the AC. if wrong i have know clue. just dont have a clue on whats going on. i had a prob like this before on a 86 daytona turbo but regulator was out and dodge had that built into the ecm. just wondering if that would be the prob.

 

you could do a charging voltage test at the battery..Use a digital multimeter,red lead to positive black to negative,start engine bring to 2000 rpm ,see what voltage you have you shoud have somewhere between 13 to 15 volts.If you do not your battery will drain,Alternator not charging enough or at all.If thats the case ,and you have already replaced your alt with the same results,may be a wiring or voltage regulation problem ,use your manual to perform what test to point you in the right direction.
Im doing a v6 to 350 v8 swap in a 84 camaro and Im sorting through the wiring on it,I got rid of the computer harness,went to a one wire alternator,I need one ignition switched hot wire for my distributor,mechanical guages, etc it gets mind boggling went you start changing things around

 

basic charging troubleshooting goes like this. first and foremost start with a fully charged good battery. if in doubt take it out and have it load tested or if its an open cell type check it's specific gravity. next, with the engine off read the voltage at the post on the rear of the alt. it should read the same voltage as you read across the battery terminals, typically about 12.6 volts. if its lower at the alt check for corroded wiring. pull the plug at the top of the alt, it should have 2 wires going to it and with the key on engine off measure the voltage at both pins on the wire socket. they both should read about 12 volts. if thats ok suspect the alt or the battery. also check to make sure your engine grounds are ok. the CS alt uses its case for its ground. the voltage reg is internal so there is no additional crap to worry about. keep us posted.

 

how do i know which alt i have. has a big wire leaving the back and above it is a plastic plug with two wires coming out of it. thanks for the help.

 

Most likely it is a CS series alt. Go to www.alternatorparts.com and they offer a free online service manual. You can look at it and compare it to what you have.