Yes I searched before posting, left to more confused. My 99 blazer has a 1 wire alternator, nothing fancy right? Puts out 14 volts cold but 12.8 - 13.2 hot and when i hit the power window with the a/c running the gauge drops. I've updated all the battery cables. I thinking I have an alternator about to take a dump

 

So by 1 wire, you mean a +12V 10ga wire + another smaller wire right? If that is the case, then the problem is likely due to a problem with how the PCM is controlling the alternator. This can sometimes be caused by an internal problem with the PCM that causes a delay in the field control signal to the alternator. One thing you could try is a rewire on the alternator to turn it into a battery reference control rather than a pulse width modulated field control as it is now.

Convert Alternator from PWM to Battery Reference

Since you only have the one wire already in the 'B' cavity of the connector, you only have to add the wire to the 'D' cavity that will run back over to the B+ stud on the back of the alternator.

 

So the one wire is coming from the PCM. I'm going to wire the internal reg for voltage all the time but its doing nothing until the alt is spinning??
I was idling for 45 mins with a/c head lights blower running and hit the window....died. Had to jump it. I may get an AD244 tomorrow and end it...want electric rad fans but gonna need juice for those.

 

Yes, the alternator in your truck is PCM controlled. You could take the alternator into a decent auto store and have it tested.

You wouldn't be disappointed by a AD244 swap though.

 

Check out Painless #30705 Simple picture and instructions