New member here. Picked up an 87 Blazer to relive the old days, alternator was not charging, replaced, made it a few miles down the road and it quit charging again. As memory serves me it has an intermal reg, and there should be nothing other than itself to keep it from charging. Ideas are more than welcome. Thanks

 

Start by checking the grounds. Could be a ground issue, could be an issue with the power cable from the alt to the battery.
You even could have gotten a bad replacement, would not be the first time that has happened.

 

Thank you, I will do that. May be overly cautious but didnt want an underlying short causing the alt to fail, and not be in the right mind. When I put the reman on it was charging 14.3. Went down the road and back, guage dropped and meter is 11.8v. Thanks again.

 

The gauges in these trucks are known to be pretty inaccurate also. I would return the alt and get a different one first just to rule that out as a problem

Then I would start looking at the grounds. There is one that leads from the alt to the back of the drives side head, and one from the battery to the frame.

And then another from the battery to the core support I believe.