So went to change my alternator today I had a 99 disco alternator I had rebuilt couple years ago figured it would go nicely with my new battery.
look at the pulley size. My oem 2004 is a bit larger than the 99 disco.
pulley won’t even go on the 99 alternator as there is no meat for the nut to grab.

does this mean I have to get a earlier thinner belt ??

 

03-04 = Valeo 120AMP alternator & 99-02 = Bosch 130AMP alternator. Two totally different units to be honest. Belt size = the same so keep the pulleys on the proper units and you should be fine with the swap.

 

you sure ? That belt rides pretty tight on the smaller pulley

 

Yep, same-o same-o. Tight isnt a problem. You've got the same number of ridges there, and that's what really counts. 99-02 and 03-04 call for the same belt, and I run the same belt on both.

 

With the pulley being smaller does it put out less voltage??
this alternator is putting out 12-13 volts at my ultraguage

 

Just eyeballing it, but the diameter looks the same. Sure the heigth is different, but that doesn't affect charging and probably just alternator specific...ie...different brand...different housing...different pully. So, to answer your question...no...it should be charging between 13.6/14.2 at idle, with load (lights, heater fan high, etc).

 

Ya something is off here. That alternator was on a 99 disco I had parted out. It looked new that’s why I kept it.
however I don’t think that’s correct. My belt was starting to shread That pulley is way small and it’s only putting out 12.4 volts there is no markings on it


one thing to note. The alternator bolts come out much easier when truck is cold. I tried removing the bolts while everything was hot and I thought I was going to snap them I guess the metal heats up and expands aluminum doesn’t

 

Looking at Rock auto for alternators for a 99 disco and 04 disco. They list some at 120 amp 130 amp and even have a bosh 150 amp

one thing in the discription is they list some at 12 volts and some at 14 volts

I guess this is a 12 volts weird

 

There are 6 volt, 12 volt and 24 volt systems...never heard of a 14 volt system in my entire life.

If alternator is not charging in range mentioned...it is not working properly.

 

Just saying rock auto lists the alternators at 12 volts and 14 volts