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Estimates last updated October 16, 2025

BMW 840i Alternator Replacement Cost

The average cost for a BMW 840i Alternator Replacement is between $1,594 and $2,025.

Labor costs are estimated between $354 and $519 while parts are priced between $1,240 and $1,506.
This range does not include taxes and fees, and does not factor in your unique location. Related repairs may also be needed.

For a more accurate estimate based on your location, use our Fair Price Estimator below.

Alternator Replacement

What is an alternator?

The battery gives your car the charge it needs to get started, but it has a finite amount of storage. This creates the need for a built-in battery charger — that's where the alternator comes in. The alternator charges the battery and powers the vehicle's electrical system when the engine is running. It provides power to the starter motor, lights, stereo and more.

How does the alternator work?

The alternator is mounted on the engine, and creates power when it's turned by the serpentine belt or drive belt. As it spins, it creates electricity, and the built-in voltage regulator and rectifier are responsible for ensuring the current is correct for the vehicle. The alternator produces an alternating current (AC), which is changed to usable direct current (DC) by the rectifier diodes within the alternator.

What are the symptoms related to a bad alternator?

If the alternator fails, the dashboard battery warning light will turn on while you drive. Soon after, all electrical components will begin to lose power, the vehicle will stall, and a jump start won't work. If the alternator's bearing fails, it can cause a grinding noise that changes with engine speed. » More symptoms of a bad alternator

Can I drive with an alternator problem?

A vehicle with a weak alternator can be driven to a repair shop, but if the alternator has completely failed, the car will need to be towed.

How often do alternators need to be replaced?

BMW 840i Alternator Replacement Cost by Year

The average cost for a BMW 840i Alternator Replacement is between $1,594 and $2,025 but can vary from car to car.

BMW Alternator Replacement Cost Estimates

The average cost for a Alternator Replacement is between $1,594 and $2,025 but can vary from car to car.

Alternator Replacement

Jump to:Cost estimates by year Related OBD codes Cost estimates by vehicle

What is an alternator?

How does the alternator work?

What are the symptoms related to a bad alternator?

Can I drive with an alternator problem?

A vehicle with a weak alternator can be driven to a repair shop, but if the alternator has completely failed, the car will need to be towed.

How often do alternators need to be replaced?

BMW 840i Alternator Replacement Cost by Year

The average cost for a BMW 840i Alternator Replacement is between $1,594 and $2,025 but can vary from car to car.

Alternator failure is fairly common, but an alternator can last well over 100,000 miles without incident. Harsh driving conditions and custom power accessories can shorten the life of an alternator.

How are alternator issues diagnosed?

When there is any failure in the starting and charging system, the entire system must be tested. Repair shops use professional test equipment that checks every component simultaneously and definitively. If the alternator is the problem, it will be identified.

How is an alternator replaced?

When replacing the alternator, the technician must remove the battery cables to prevent electric shock. The accessory drive belts or serpentine belts must be removed from the alternator, along with electrical connectors and several bolts. Once the bolts are removed, the alternator is free from the alternator brackets, and can be removed. Replacement is in reverse order, and proper torque must be applied to prevent damage. The vehicle will then be retested.

RepairPal recommendations for alternator issues

Because the alternator requires the removal of the serpentine belt, this is a good time to replace that belt if it's worn, or the service interval has been reached. If the battery cables have physical damage or extensive corrosion, they should be replaced as well.

What to look out for when dealing with alternator issues

On some cars, it can be hard to access the alternator, and that can play a significant role in the repair cost. In some cases, suspension components, drive axles, cooling fans and even bumpers must be removed. If the vehicle has after-market electrical components installed, the new alternator should be strong enough to handle the additional power demands.

Can I replace the alternator myself?

If the alternator is tucked away and hard to get to, the replacement should be left to a professional technician. If the alternator is more easily accessible, and you have a good understanding of the starting and charging system, you should be able to diagnose and repair this problem yourself.