15 Oct How to Change Your Altenator

When you need to change your alternator be sure you are replacing it with the same model as you are taking off. Some engines will shake apart certain models if they are used. Also remember if you up your alternator to a bigger model you will have to update your cables with it so they will carry the current.

Ok first thing to do is disconnect the batteries, I usually remove all the cables and clean them and the battery posts. Remember not to make any sparks that could cause battery explosion or damage to the vehicles computer system.

Once the batteries are disconnected go to the alternator and loosen the top tensioner bolt if equipped, and you may have to loosen the tensioner bracket engine mount bolt as well, then you should be able to push on the alternator and remove the belt or if you have a spring loaded tensioner, using a ratchet pull on the automatic tensioner and pull the belt off to the side.

Now note where the wires are connected to on the rear of the alternator write them down on a piece of paper for reference. Some only have a red and black, some also have a two prong plug, some also have a smaller wire on a smaller terminal. Once you have found were the connections go, loosen them and remove them from the terminals.

Now remove the top mounting bolt or bolts and then the bottom mounting bolt. Then remove the alternator from the mounting base, lay the alternator on a bench and using a 1/2 inch impact with a 15/16 socket remove the retaining nut from the pulley. You may have hold onto the pulley when you burp the impact. Now pull the pulley off the alternator.

If your pulley is stuck, hold the alternator up by the pulley and tap the shaft with a brass drift. This usually works, but there are cases were it’s stuck even worse, so you may have to heat around the pulley, perhaps to 200 degrees and have water next to you, when you’ve reached your temp pour the water where you’ve just heated then again hold it by the pulley and hit the shaft with a brass drift.

Repeat above steps until pulley is removed, once you have the pulley removed place the pulley onto the new alternator and torque to 75-85 ftlbs, then set alternator into the mounting bracket on the engine and install the bottom mounting bolt, then the top one. Hook up your cables to the terminals and tighten them. Then put on the belt and if you have the manual tightener turn the adjusting nut out until you start to feel tension, use a belt tension gauge to get the proper setting.

If you don’t use a gauge you may damage your alternator bearings, if you have the automatic tensioner use the ratchet and pull back on it so you can put the belt on the alternator. Once the belts are on and the tension set tighten the top and bottom mounting bolts. Then go and hook up the batteries positive first and negative last.

Once you are finished start the truck and test the output of the alternator. Also before I forget, before hooking up the batteries you should load test the batteries to make sure they are in good shape, they may have wrecked your alternator in the first place if you have a bad one. The batteries need to be at 12 volts and tested with a heavy load tester.

Make sure your batteries are fully charged before putting your truck back in service, otherwise your new alternator will get overworked and probably fail in a short time.