How Long Does It Take to Replace An Alternator

Having some mechanical skills goes a long way when it comes to car maintenance. Many repairs are expensive—and usually unexpected. The question of how long does it take to replace an alternator is that it depends on the make and model of your vehicle. It all boils down to access. Newer cars and smaller ones can pose a challenge for even the experienced DIYer.

Signs of a Bad Alternator

The purpose of this part is to keep your battery charged. As you drive, it replenishes what you’ve used to turn over the engine. The signs that something is amiss involve power issues. You may notice that your interior or dashboard lights are dimmer because they’re not getting enough juice. It’s essential not to delay replacing your alternator. You could get stranded if it fails and your battery is dead.

The latter problem will only add to your costs. Automotive batteries are lead-acid based and can’t handle repeated deep cycling, unlike lithium-ion ones which can. They will shorten its lifespan and set you up for even more hassles down the road. Besides that, they cost almost as much as the alternator.

What You Need to Replace an Alternator

For the most part, you can replace the part without any special tools, depending on whether your vehicle has a serpentine belt. The supplies you’ll need include:

  • Open-end wrenches
  • Socket wrenches
  • Belt tensioner (if necessary)
  • Pry bar or large screwdriver (optional)
  • Voltmeter
  • Memory saver (optional)
  • Replacement part
  • Work gloves

The last item is the deal-breaker. It won’t have you scanning used car values or new car prices, but sometimes it’s expensive, again, depending on the model. You can expect to pay $200 or more just for the part. The belt tensioner will run about $50-$100. The fact is that this job won’t cost you as much in labor as it will for the alternator.

The cost of taking it to a mechanic depends on the make and model. It’ll run around $300 to $400 for an older Ford truck. A newer foreign SUV will send the cost north of $500 and maybe even as high as $1,000.

The job requires an intermediate skill level. If you know your way around cars, it’ll take you well under an hour. It all rests with what you need to do to remove the old one. Like any repair, there are other things you should check while you have access. You should examine any belts for wear. Unlike the alternator, some like the serpentine one take you off the road immediately and necessitate a tow.

Guide to the Repair

You should begin by testing both the battery to find out if you need to charge it before doing the repair and the alternator to make sure it is indeed bad. If all is good, you’ll get a reading around 12.5 volts for the former with the vehicle off and about 14 volts when started. Then, get the figure with the voltmeter with some accessories running like your light.

If it stays the same or spikes, then you’ve got a problem, and you’ll need to replace it. Likewise, if the battery has less than a 50 percent charge, you’ll need to get it up to 100 percent before you start the repair. If you have a newer vehicle, you should also use a memory saver to retain your car’s presets. You only have to reset your clock with older models.

Do yourself a favor and check the belt before you start wrenching on your car. Older models will have V-belt and newer ones, a serpentine belt. Examine it for cracks and wear. If it looks sketch, pick one up at the parts store when you get the alternator to save you a trip.

While you’re at it, also inspect the battery for corrosion. Clean the posts with a cloth. There are also products that you can get that will prevent it. You can also put felt disks on the post that will also do the job. Also, examine the cables for any signs of wear. The rubber casing will dry out over time. It’s easy to swap out new ones. And you can get them for under $20.

Disconnecting the Battery’s Power

The next thing you must do is disconnect the battery. Metal tools in your hands and a live electrical connection don’t play nice together. You could also do more damage and add to your costs. Removing the negative cable is sufficient. You needn’t remove it or take off the positive one. Taking off one will break the current and keep you safe. It only takes a single milliamp before you’ll feel it.

Taking Off the Alternator

Then, do the same thing with the alternator’s power cable by removing the bolt with either a socket or open-ended wrench. Disconnect the harness next. Now, it’s time to loosen the belt. Again, it depends on the vehicle. You may just have to unscrew the hardware holding it in place or use the belt tensioner tool. If you noticed damage, you'd also have to pull out the belt.

Be careful if you’re removing a serpentine belt. Tension is the operative word here. Don’t let it snap back and hurt you or damage any other parts under the hood. Once it’s loose, you can take it off and continue with the repair.

Once you’ve completed these steps, you can slip off the old alternator from its housing. Take a moment to compare the new and old ones to make sure you have the right part. Look at how the holes align and the location of the connections. After all, mistakes happen.

Replacing the Old With the New

The new alternator should slide into place easily. Take care to avoid pinching any wires. Don’t force it into the spot. Work it in gently. If you had to replace a belt, now is the time to install it. Then, tighten the bolts. Use a pry bar if there isn’t a pulley applying tension to the belt. Ideally, you want to find the Goldilocks spot of not too tight or not too loose. About one-half inch of play is the sweet spot.

Next, put the harness and power cable of the new alternator in place, following the same steps in reverse that you took to take the old one away. Look over everything again and note the tension of the belt. Make sure that the bolts are tight and that you haven’t left anything inside the engine compartment.

Reconnect the Battery and Test the Job

Now is the big moment when you see whether you’ve done it right. First, reconnect the negative cable back onto the battery. Make sure that both of them are tight. Turn on your vehicle and get a reading from the voltmeter. If all is well, it’ll be around 13.5 with nothing else running. Mechanically, you’ve done everything right. The next step is the follow-up to make any corrections.

You should check the tension of the belt after a few days of driving the vehicle to make sure that it’s still right where it should be. Then, pat yourself on the back for a job well done with a sigh of relief that you don’t have to shop for a new ride on Car Finder. Don’t forget to restore your vehicle’s presets with the memory saver, following the device’s instructions.

The crucial thing when considering how long does it take to replace an alternator is that it’s an opportunity. You’ll have the chance to check other components under the hood and save you the hassle of something happening on the road. Even though it’s a repair, it’s also preventive maintenance for the other parts that could fail and strand you.