Alternator Replacement Cost in the UK

Alternator replacement typically costs between £200 and £600 in the UK, with the average bill sitting at around £350.

The alternator itself usually costs between £120 and £350 for a typical car, although larger or premium models can need more expensive units. You’ll then need to factor in labour, which can range from one to three hours depending on where the alternator sits in the engine bay.

Some are relatively easy to reach, while others sit behind or underneath several other components. In those cases, you’ll naturally pay more for labour.

What does an alternator actually do?

Your alternator plays a pretty important role. Once the engine is running, it generates electricity to power the car’s electrical systems while also keeping the battery charged.

It’s easy to confuse alternator problems with battery problems because the symptoms can be very similar.

If your alternator stops charging properly, even a perfectly healthy battery will eventually go flat. That’s why it’s worth testing the charging system before automatically replacing the battery.

What are the signs of a failing alternator?

Alternators don’t always fail suddenly. You might notice a few warning signs first, including:

• Battery warning light while driving: This is one of the clearest signs that something isn’t right with the charging system.

• Headlights getting brighter and dimmer: You might notice the lights dimming while idling and becoming brighter when you increase the engine revs.

• A battery that keeps going flat: If you’ve charged or replaced the battery and it goes flat again shortly afterwards, the alternator could be the real problem.

• Whining or grinding noises: Worn alternator bearings can start making noticeable noises from the engine bay.

• Electrical problems: Flickering dashboard lights, slow electric windows or a radio that cuts out can all appear when the system voltage drops.

• A burning rubber smell: A slipping or damaged auxiliary belt can produce a noticeable burning smell and may affect the alternator.

The good news is that testing the charging system is quick and straightforward. A garage or battery specialist can usually check it within a few minutes.

As a rough guide, a healthy charging system will often show somewhere around 13.8 to 14.4 volts across the battery while the engine is running, although modern smart-charging systems can vary their voltage considerably.

Getting the system tested before buying any new parts can save you from replacing a perfectly good battery or alternator.

Should you buy a new, reconditioned or used alternator?

You don’t necessarily have to buy a brand-new alternator.

A new original-equipment or high-quality replacement unit will generally cost the most, but it’s also likely to give you the most peace of mind.

A professionally reconditioned alternator can be a good middle ground. These often cost around 30 to 50% less than a new unit and may come with a one or two-year warranty. Just make sure you’re buying from a reputable manufacturer or supplier rather than choosing purely on price.

Used alternators from breakers are the cheapest option, but their history and remaining lifespan can be difficult to know. They may make sense on an older, low-value car, but you might prefer something with a warranty if you rely on the car every day.

It’s also worth asking the garage to inspect the auxiliary belt while replacing the alternator. If the belt is already worn and needs to come off during the job anyway, replacing it at the same time could save you trouble later.

Can you drive with a failing alternator?

Possibly, but you don’t know how long you’ll have.

Once the alternator stops charging, the car starts relying entirely on the electricity stored in the battery. When that runs out, the engine will eventually stop.

How quickly this happens depends on the battery’s condition and how much electricity you’re using. Driving at night with the headlights, heater and wipers running will drain the remaining power much faster.

Modern cars can also start shutting down electrical systems as the voltage drops before eventually stalling.

If the red battery warning light comes on while you’re driving, avoid unnecessary electrical equipment and head somewhere safe. If you’re close to a garage, you may be able to get the car there, but don’t assume you have a certain amount of driving time left.

Stop-start cars and smart alternators

Alternator replacement can get slightly more complicated on newer cars with stop-start technology.

Many of these cars use smart charging systems that vary how and when the alternator charges the battery. For example, the system may increase charging while you’re slowing down and reduce it at other times to improve efficiency.

This means the replacement alternator needs to match the specification of the original unit. Fitting the wrong alternator could lead to charging problems, warning lights or other electrical faults.

Stop-start cars also commonly use AGM or EFB batteries, which cost more than traditional lead-acid batteries. Some vehicles require the garage to register a new battery with the car’s battery management system after fitting it.

Because of this, a garage will usually need your exact registration or vehicle details before giving you an accurate price.

Alternator FAQs

How long does an alternator last?

An alternator can commonly last somewhere around 100,000 to 150,000 miles, although there’s no fixed lifespan.

Driving conditions and electrical demand can make a difference. Regular short journeys and running lots of electrical equipment can put more strain on the charging system.

Ultimately, some alternators will fail much earlier while others can last for the life of the car.

Alternator or battery: how can I tell which one is faulty?

The symptoms can overlap, so testing is the easiest way to know for certain.

If you jump-start the car and it soon cuts out again while you’re driving, the alternator or charging system could be the problem.

If the car runs normally once started but struggles again after sitting overnight, the battery may be more likely.

However, these aren’t foolproof tests. A quick battery and charging system check will give you a much clearer answer.

Does a new alternator need coding?

On most cars, replacing the alternator itself doesn’t require coding.

However, some newer vehicles use more complicated energy management and smart-charging systems. The garage may need to carry out a reset or other diagnostic work after fitting certain components.

If the battery also needs replacing, some cars require the new battery to be registered with the vehicle.

Can a failing alternator damage anything else?

It can cause other problems if you ignore it for too long.

Constant undercharging can shorten the life of the battery, potentially leaving you with both an alternator and battery replacement bill.

Mechanical problems can cause issues too. For example, if an alternator bearing or pulley seizes, it can damage or throw off the auxiliary belt.

Getting a suspected alternator problem checked early can help prevent a relatively straightforward repair from becoming more expensive.

Can I replace an alternator myself?

It depends heavily on the car and your mechanical experience.

On some older cars, the alternator sits near the top of the engine and is relatively straightforward to access. A competent home mechanic with the correct tools may be able to replace it.

On other cars, reaching the alternator can involve removing several components or accessing it from underneath the vehicle.

If the job requires significant dismantling or you’re not confident working with the car’s electrical and belt systems, paying for professional fitting is usually worth it.

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