2006 Chevy Trailblazer LS 4.2L

I have a 2006 Chevy Trailblazer, I just replaced my bad alternator to find that the idle is still bad.  My lights dim when my A/C is on and it feels like it is going to stall.  I checked the plug to the Actuator Solenoid and did not find any oil.  Now, when I turn my wheel all the way to the right/left, it almost stalls out and my inside volt meter drops quickly.