How-To: Replace an Alternator

Strapped for cash this holiday season? Replacing an alternator can cost you several hundred bucks at the local repair shop, but it's one of the simplest repairs you can do at home. With a few tools and about an hour you can swap it out yourself -- and keep your dough in your pocket where it belongs.

Note: As this is a Craftsman-sponsored project, you'll notice a number of Craftsman tools in the photos, including Cross Force Wrenches. But here's a secret: we already owned 'em all. They're the same tools we'd have used if they weren't sponsors. Really!

First and most importantly: disconnect the battery. There may be several wires or just one wire on your alternator, but rest assured that one of them is hot. If you don't disconnect the battery, you're very likely to end up grounding a live wire during the process. This causes cause all manner of bad things to occur -- not the least of which is giving you quite a shock.

Now that the battery is out of the way disconnect the wire or wires from the back of the alternator. This is usually a very simple process but if you're unsure as to where they go, label them as you take them loose.

Every project has a tough spot, and this is the tough spot for alternator replacement: remove the belt from the pulley. Somewhere on your vehicle there is a tensioner pulley. You'll need to move it enough to slip the belt off the pulley. Our '95 GMC has a standard spring-loaded GM tensioner that required us to pull it back with a wrench. On some vehicles you'll find screw-type or rod-end type tensioners that apply tension by turning a bolt through threads to increase/decrease the length of a rod. In this case, just turn the bolt/rod-end with a wrench or socket until it releases enough tension to allow you to remove the belt.

In our case we grabbed a Craftsman 17mm Cross Force wrench and pushed hard. Normally that would be a pretty painful experience, but the Cross Force was designed for just such a situation. There's a 90-degree twist in the middle of the Cross Force wrenches, so you end up pushing on a flat surface. The result: we could push harder without discomfort. So we just laid into it and the belt came free.

Once the belt is off just remove whatever bolts connect the alternator to the bracket and you're good to go. Our model required the removal of three bolts: one at the front and two at the rear.

With the old alternator in your hand you're half way home. You'll likely find getting the new one back in goes much faster since you already know what size the bolt heads are and where everything is.

Examine the replacement unit before reassembly and make sure it will work for your application. Our replacement was a junkyard find so it is great deal dirtier however it has the advantage of actually working -- a significant improvement over our previous busted unit.

To complete the project just reverse the removal steps paying careful attention to belt routing and tensioning. Hell, even if you bought the set of Cross Force wrenches for the job you'd still be hundreds ahead of the cost of what a shop would charge -- and you get some new tools out of it. We can think of far worse outcomes.

Cross Force Wrenches