In the mid '70s, GM began offering its SI-series (Systems Integrated) alternators, which not only delivered more amperage but did away with the externally mounted voltage regulator and its messy ...

Your Blazer is most likely equipped with a Delco 10si alternator, as most GM cars and light trucks used the 10si through the 1970s. These came in a variety of amp ratings depending on the vehicle ...

07GM SI alternator internal regulators can be ... repair or replace the entire alternator. Late-model GM CS alternators don't have serviceable regulators; the entire unit must be replaced.