Some of our preliminary notes for the alternator of the Astra. These might help one get started with research; there may be older and newer part numbers. Double check with the dealer using your VIN to confirm fit!

* Manual transmission?
93190829 - Alternator with steel pulley (RockAuto shows a BOSCH AL8903N, not sure if that includes a pulley and looks like China made)
93174477 - Basic Steel pulley

* Auto transmission?
93188158 - Alternator with clutch pulley - (6204218 13222933)
55560294 - Clutch pulley - catalogue number: 12 04 484

There are a few 93188158 at US dealers. But we saved some money still going OEM (93190829 alternator made in Spain and a new INA clutch pulley (F00M147880)).

Alternatively, it might be easier and cheaper to have a local shop rebuild your alternator.

We suspect all 2008 Saturn Astras shipped with a basic steel alternator pulley. But GM eventually issued a clutch-pulley for the automatic transmission models (maybe in a service note).

Our automatic transmission Astra had squeaky accessory belts. And it ate belts and tensioners quickly. Eventually, we installed a clutch pulley on the alternator which resolved said problems. We used the CTA 8088 Bosch Alternator tool for the pulley. We read that pulley can be changed on the car but we couldn't figure that out as there's no space. So we removed the alternator from the car. Removing the data cable and squeezing the alternator out of the car were "challenging." Swapping the pullies was easy.

 

A few people on Facebook installed the wrong aftermarket alternators and the cars did not work properly. One of the forum's techs said the manual transmission cars might have different alternator (e.g. amp ratings, clutch-pulley....?).

So use your VIN number (and the part numbers on your installed alternator) to confirm correct fit; I would ask the dealer to avoid redoing the (somewhat painful) install.

- I think the replacement alternator for our AUTOMATIC transmission Astra typically is 120A with a clutch-pulley.

- The MANUAL transmission cars were not made with the clutch-pulley and I don't know the typical amp ratings

European Astras had lots of engines so lots of alternator options. The North American cars only had the z18xer engines installed so there will not be many alternator versions.

For reference, below are photos of a well-used alternator from a junkyard (2008 Saturn Astra XE AUTOMATIC transmission) sourced from car-parts.com. We can see 120A and some part numbers on that made in spain bosch alternator. The owner had the original steel pulley, so had not upgraded to a clutch-pulley (see TSB 10-06-01-001).