View Full Version : 120Amp alternator pulley problem

03-08-2015, 08:02 AM
I recently picked up a 120amp alternator from autozone (it was cheaper than the 90amp), it was suppose to be a direct fit. Everything was fine until I started the car, the belt now jumps off the lower pulley as soon as I start it. It seems that the alternator pushes the pulley out about 1/4" more than the stock one and therefore causes the belt to jump. Anybody have any suggestions short of getting a new alternator? I need this fixed today so I can't order a different pulley or a different alternator unless absolutely necessary.

A1 A2 German
03-08-2015, 08:44 PM
You have to use the opposite pulley then what's on your car now.

If you used the 90amp pulley on the 120 amp alternator you need to get your hands on the the 120amp pulley.

Or, it's:

If you used the 120amp pulley on the 120 amp alternator you need to install the 90amp pulley.

The physically size of the alternators are different, hence the different sized pullies between the two which make up the difference when they line up with the serp system.

03-08-2015, 08:47 PM
I realized that after I posted, thanks for the insight though. I ended up returning the alternate and ordering the 90 amp since I really don't need the larger one anyway, and since the alternator is easier to source than the correct pulley.

A1 A2 German
03-08-2015, 09:07 PM
You also lose some power with a 120amp too and yes! The 120amp pulley is like $72! Sometimes you luck out and the pulley comes with it, others time not.