The alternator or drive belt is a vital component that keeps modern cars running.
It helps convert mechanical energy from the engine into electrical energy that powers the alternator, air conditioning, and other essential systems. If the belt fails, you might face issues like a dead battery or overheating.
But how can you tell when you need a new alternator belt?
Read more to discover how an alternator belt works, how to tell if it’s failing, and the replacement costs you might incur.
This Article Contains:
- What Is an Alternator Belt?
- 9 Symptoms of a Faulty Alternator Belt
- How Much Does an Alternator Belt Replacement Cost?
- Is the Alternator Belt the Same as a Serpentine Belt?
- 3 FAQs about Alternator Belts
What Is an Alternator Belt?
The alternator belt (sometimes called a serpentine belt, drive belt, or fan belt) runs from the crankshaft pulley to the alternator pulley.
It transfers rotational energy from the crankshaft to the alternator as it spins. This, in turn, helps the alternator generate the electrical energy needed to recharge the battery and power every electrical accessory in your vehicle.
Here’s a breakdown of how it works:
- Your car’s crankshaft has two ends. One is connected to the transmission, and at the other end are the pulley belts, chains, and gears.
- The alternator belt transmits power from the moving car to the alternator to generate electricity.
- The alternator takes over work from the battery to provide electrical energy to the electricity-powered parts of the car.
- It charges the car battery while getting the power from your car’s motion.
In some modern cars, the alternator belt also drives the oil and water pumps. But it’s not the only belt in your car. There are also other belts serving different purposes, like the V-belt and the timing belt that work to propel parts of the engine.
Note: An electric vehicle won’t have an alternator belt or timing belt. That’s because an electric vehicle has neither an internal combustion engine nor an alternator. So, there’s no need for any drive or accessory belt.
Now that you know what it is and how it works, let’s see how to tell if it’s failing.
9 Symptoms of a Faulty Alternator Belt
A bad alternator belt can hinder the performance of your alternator and limit its ability to pull power entirely.
Watch out for these signs of a failing alternator belt:
1. Dim or Flickering Interior Lights
The alternator belt keeps the electricity that powers the interior lights of your car running. So, once the belt is bad, you’ll notice some irregularities with the lights, like flickering or dimming.
2. Air Conditioning Doesn’t Work
Your air conditioner can fail if you have an alternator belt issue.
The belt runs over the crankshaft pulley that powers the air conditioning compressor. If you have a broken serpentine belt or faulty belt tensioner, the pulley won’t spin, and the compressor won’t work — leaving you with a malfunctioning air conditioner.
3. Car Engine Switches Off
Imagine being in motion, and the car engine suddenly goes off. That would be devastating, especially on a highway or in the middle of the road. A faulty alternator belt or belt tensioner may cause this scenario since your car engine won’t get enough power to run the combustion and transmission parts.
Sometimes, a worn-out alternator belt transmits a low electric charge to the engine. This leads to a super-low acceleration power if it doesn’t cause a complete engine stop.
4. Squealing or Rattling Belt Noises
A loose alternator belt may cause flapping or squealing noises as the car operates, especially in colder weather and climates. This noise comes from the alternator belt not being properly seated in the system or improper belt tension, which may be due to a failed idler pulley or tensioner pulley.
Conversely, you may hear rattling if you have a torn, broken, or misaligned belt.
Note: It may or may not be accompanied by a lit battery warning light on your dash.
5. Dead Battery
The alternator charges your car battery while in motion. Once the battery gets the car running, the alternator takes over the electric power transmission in the vehicle.
While the car runs, the alternator charges the battery while powering other parts.
However, it’s a different story when the alternator belt is faulty. The battery now has to power your car engine while not being charged. The battery dies quickly this way. So, a dead car battery is one of the principal but unpleasant ways to discover that your alternator belt is broken.
6. Power Steering Issues
Modern vehicles may have a power steering pump that runs based on the movement of the alternator or serpentine belt. So, a broken or faulty belt can prevent your power steering from working. This could cause a loss of control at high speeds, leading to accidents on the road.
7. Engine Overheating
Another engine accessory that the alternator belt may power is the water pump, which enables the flow of coolant.
When the belt breaks or goes bad, it can impact the functioning of the water pump in some vehicles. This may prevent coolant flow, leading to soaring temperatures and overheating in the engine bay.
8. Smell of Burning Rubber
The alternator belt is made from reinforced rubber. When the belt wears out, it begins to smell like burning rubber. This is caused by the heat generated during the continuous friction that propels the energy transmission in the car. This heat melts the rubber, producing the smell.
Note: If you smell burning rubber from the engine compartment, you’ll mostly need a new belt.
9. Cracks or Discolored Spots on Belt
Despite being made from tough reinforced rubber, even modern serpentine belts can wear out with age or due to bad belt tension — developing discolored spots or cracks. These cracks can worsen if you ignore regular servicing, and your belt could snap.
If you notice these signs, you might need a belt replacement.
How Much Does an Alternator Belt Replacement Cost?
An alternator belt replacement can cost between $100 to $200. However, these costs may vary depending on the vehicle model, location, mechanic’s labor rate, and replacements needed.
Here are estimates for the belt and other related parts (without labor costs):
- Alternator belt: $15 to $80
- Idler pulley: $40 to $90
- Tensioner pulley: $20 to $240
Note: Using OEM parts can increase the cost of these replacements.
Next, let’s clarify any confusion about the alternator belt and serpentine belt.
Is the Alternator Belt the Same as a Serpentine Belt?
Your alternator belt is a serpentine or drive belt that helps energy flow to your engine — regulating and optimizing its function.
However, not all serpentine belts are alternator belts. In some cases, they can be used for specific engine assemblies and purposes that would place them into separate categories.
For example, some old cars may have separate belts, like an accessory belt for the power steering pump. Refer to your owner’s manual to know the separate belts used in your car, which may include a timing belt and fan belt.
However, these terms are used synonymously across the field in modern vehicles, as these situations are rare.
Have more questions about alternator belts?
We’ll tackle them next.
3 FAQs about Alternator Belts
Below are answers to some common queries about alternator belts:
1. How Long Does an Alternator Belt Last?
Modern serpentine belts are rated to last between 50,000 and 100,000 miles or 4 to 7 years of use.
However, you should always have an old belt inspected when performing routine maintenance, like an oil change or tire rotation, and take note of its condition. If you notice any symptoms of a bad serpentine belt, it’s best to have a professional mechanic install a new belt.
2. Can I Drive with a Broken Alternator Belt?
No. If you have a broken serpentine belt, stop driving and have a mobile mechanic come to you. The car engine would overheat quickly since there’s nothing to power the water pump. This may cause the car to come to a halt and potentially severe engine damage.
If it’s an emergency, you might be able to drive for up to 90 minutes with a bad serpentine belt. To go a relatively extended distance, you should:
- Put off the vehicle systems that use electricity, such as the air conditioning, lights, radio, windshield wiper, etc. This would help conserve the car battery’s energy. In this condition, you would have a fair chance of not getting stuck on the road.
- Avoid driving in congested spaces or traffic at all costs. Slow traffic flow drains the battery quickly.
- Drop by an automotive repair station first for a serpentine belt replacement.
3. What Are the Benefits of Replacing Your Car’s Serpentine Belt?
Replacing an old belt ensures your battery will charge and last longer. So you won’t have to worry about a sudden breakdown.
You’ll also enjoy the benefit of preventing engine accessory malfunctions.
Fix Alternator Belt Issues with AutoNation Mobile Service
The alternator belt doesn’t go down alone when it fails — it affects various auto parts connected to your vehicle’s engine. Hence, always look to service or replace it at the earliest signs of wear. Your vehicle systems will thank you for it.
Looking for reliable, convenient auto repair?
Let the experts at AutoNation Mobile Service take care of it for you!
We’re a mobile car care company offering comprehensive auto services with upfront pricing and a 12-month, 12,000-mile repair warranty.
Contact us to get a serpentine belt replacement or any other auto services, like tire rotation or tire repair, completed in your driveway!