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Your alternator provides electricity to all the accessories in your vehicle, but how does the alternator get its motivation? In older cars, there were several belts that were connected via pulleys to the crankshaft of the engine, and they would power all the engine accessories like the alternator, power steering pump, air conditioning compressor, and others. Newer vehicles use a single long belt that snakes through all the various pulleys called the “serpentine belt”. Older vehicles used belts that had a thick, v-shaped cross-section, and so they were called “v-belts”. Many newer serpentine belts have a cross-section with multiple small vees, and so you may run across the term “micro-V belt” when searching for parts.  

What does a new belt for alternators cost? Learn more about service intervals and repair costs for alternator belts.

What Does the Alternator Belt Do? 

Your serpentine belt is moving whenever the engine is on because it powers essential systems like the alternator, the air conditioning, and even the engine coolant pump, known as the water pump. Even if your car is idling, these systems need to be working so the belt never stops. As you can imagine, this creates wear on the belt and it is definitely an item that you want to replace at regular intervals.

How Much Can I Expect to Pay for My New Belt? 

The most expensive common belts cost about $50-60, but you can sometimes find belts for $10, too. There are many good-quality belts available in the $20-$40 range. If you decide to replace the idlers and tensioner pulleys at the same time, you can get kits in the range of $80-$150 that include all the parts necessary to give you peace of mind that your serpentine belt will be reliable for years to come.

Why Should You Replace Your Alternator Belt? 

How often should you replace the serpentine belt? All belts have a recommended service life, and with modern rubber and manufacturing technology those limits have become pretty high. Most new serpentine belts are rated to last between 60,000 and 100,000 miles, but there are good reasons to replace the belt sooner than that. Here are a few: 

  • If the belt is showing signs of wear like fraying on the edges or cracking on the grooved side, that’s a sign that you may want to replace it. 
  • If the belt has discolored spots, that may be a sign that it is breaking down.
  • If your engine’s belt has become contaminated with fluids like oil or engine coolant, you’ll want to keep an eye on it. Modern rubbers are very resilient, but fluids can be corrosive or cause the rubber to swell.  
  • If you are replacing your alternator or other engine parts that connect to the serpentine belt then it makes sense to replace the serpentine belt at the same time since everything is taken apart already and the cost of the belt will be small, compared to the costs of other parts and the labor involved. 
  • Some serpentine belts are “stretch belts” which must be replaced any time you remove it from the vehicle, so if you have a stretch belt and take it off for any reason then you need to replace it. Check your car’s manual for that information. 

What Other Parts of the Car Does that Effect? 

Your serpentine belt winds its way through many different pulleys in the engine bay, providing power to a host of different and essential systems. Many vehicles use a belt-driven water pump to provide coolant fluid circulation throughout the engine. If the belt breaks while the engine is running, your engine temperature will rise, the car will overheat, and the result could do permanent damage. Another potential safety issue related to the serpentine belt is your power steering, but this is becoming less common because many modern passenger vehicles have switched to electric power steering. Your alternator, though, is guaranteed to be powered by the serpentine belt, and if it breaks your vehicle will only run until your battery is exhausted.  

Are There Other Parts You Should Replace at the Same Time? 

If you decide to replace your serpentine belt for any of these reasons, it makes sense to replace the idler pulley and tensioner pulleys at the same time because you’re taking everything apart already. Most serpentine belts have one or more idler pulleys in their run. An idler pulley is simply bolted to the engine and usually serves to change the direction that the belt is traveling so that it can maintain its contact with the pulleys attached to accessories. The other important non-accessory pulley attached to your belt is the tensioner pulley. A tensioner pulley will either have a bolt or screw that you adjust manually or it will have a built-in spring that maintains the correct about of tension on the belt. In a manual tensioner, the bearing can wear out and in the spring-loaded version, both the bearing and the spring can wear out. For many vehicles, you can get a package that includes the serpentine belt with the tensioner and any idlers that are required. Check AutoZone online or in-store to see what’s available for your car. 

Are There Different Grades or Qualities of Belt? 

Just like anything, you can get a range of serpentine belts, from very inexpensive belts to highly engineered belts designed for racing. If you replace your belt within the recommended service life interval and check it every time you pop the hood, a mid-range belt should serve most drivers.

Can I Replace the Serpentine Belt Myself? 

You’d be surprised at how many general repairs and maintenance items you can do yourself! Replacing the serpentine belt, idlers, and tensioner pulley typically requires a socket set and a set of screwdrivers, plus about an hour of work if you haven’t done it before. Don’t be afraid to try this important repair and be sure to stop in at an AutoZone store or shop online for all the tools and parts required for your project.

Keep in mind if the repair appears to be too difficult, take a look at our Preferred Shops in your area that can help you tackle the job.  

Advice, how-to guides, and car care information featured on AutoZone.com and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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