How To Measure Alternator Amps?

[badge49]

I've needed a new alternator for a long time...due to a melting spell mine had a year or so ago. I'm pretty sure I have the 90 amp. alt. With my dual batt. system, the isolator is only rated to 120 amp., so I don't want to just put any old alt. in as a replacement.

How can you tell, at the Pick-n-Pull yard, what amp. output different alt. will make? Is it printed somewhere? And will an early Explorer/Ranger alt. fit the same as my later '97?:navajo:

 

[BrooklynBay]

It's usually stamped on the alternator. Autozone has a tester for verifying it before you install it.

 

[badge49]

Ah ha... do Aerostar alts. fit Explorers? I'm hitting the Pick-n-Pull in a few.

 

[BrooklynBay]

They should.