It could also be your "big Brother" computer does not like the output of the altenator/voltage regulator. I was reading a thread on the S10 Crew Cab site, one of the members HenryJ installed a high amp altenator and it worked fine for a short while before throwing a code. He has lots of accessories winch, off road lights etc; he installed a CS144 high amp altenator and the computer had troubles with it:

Here is the link to the thread:

http://www.s-10crewcab.com/phpBB2/vi...&highlight=144

 

The guy that sold me the alternator sent me the smaller pulley. I had it installed, and i didn't have 2 change the belt. Blazer is running fine. When i have my sound system loud, the needle moves a little, but that's normal. The only thing is, that when i turn everything on, such as headlights, wipers and turn signals, it's fine, but then i add the ac, the needle moves just a little lower than 14 volts. But i consider this normal, and the truck is running fine. Also, another thing, when i have the headlights on and put on my turn signal, the P, R, N, D, light dims everytime the blinker flashes. But the needle doens't go into the danger zone anymore. So i am happy and everything worked out well. Thanks 2 all of u for giving me all the advice and for helping me solve the problem.