I would like to know how to remove the alternator

If the generator really is bad, just get someone to jump-start your vehicle. That will allow you to drive it until the battery runs down. That can be from a few minutes to half an hour, depending on how many lights and other circuits you can leave turned off. Here is a guide to help you step by step with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/how-to-replace-an-alternator

You described the belt removal procedure correctly. The spring-loaded tensioner pulley will only spring back just so far when you release it. The important point is to disconnect the negative battery cable before you put a wrench on the nut holding the large cable to the back of the generator.

One trick is to slide the belt off the generator pulley, then use a rubber bungee strap hooked to a hole in the under-side of the hood to keep a little tension on it. That will prevent it from falling off any of the other pulleys which can save a lot of time from trying to figure out how it was routed.

here is a diagram of the serpentine belt, make sure you disconnect the negative battery cable first, use the tensioner pulley to remove the belt and reinstall it. Then you can remove and reinstall the new alternator.

opps sorry Car Doc got this one.

I believe it is the alternator because I put a new battery in about a month ago. I was driving and my radio quit working then my headlights and instrument cluster dimmed and when I parked it the battery light and brake light illuminated. and the truck idled like it was losing power.

Also, would you know the exact tools needed to complete this repair on my year of Isuzu? exact wrench and socket sizes? and can I use a regular ratchet or wrench for the tensioner. I do not have a breaker bar.

I believe the tensioner bolt is a 14 or 15mm and can be done with a wrench it will just be tough to pull the tensioner back with a shorter wrench.

Okay. Thank you all so much! This will be the site I go to for answers from now on! Thank you for passing your knowledge on. I am a self taught mechanic never had anybody in my life to teach me anything about vehicles. your help is appreciated more than you know.

Glad we could get it fixed please use 2CarPros.com anytime we are here to help

Best, Ken