Battery warning light and alternator · Autobedrijf Willemsbrug Rotterdam

Battery warning light on? We test and repair your alternator

Is the battery warning light on while you drive? Or are the lights getting dimmer and does the car not start after a trip? Then the alternator is probably not charging the battery. We test it thoroughly and repair alternators in our own workshop. You hear the price in advance.

4.8 / 5 from 235 reviews | All makes | Price agreed in advance

The short answer

If the red battery warning light is on while you drive, the battery is no longer being charged, usually because of the alternator or the belt that drives it. Autobedrijf Willemsbrug at Boterdiep 11 in Rotterdam-IJsselmonde measures the charging voltage, tests the battery, checks the belt and repairs alternators in our own workshop. You hear in advance what the repair costs. We only start once you agree, and the same goes for any extra work.

Jump to: symptoms · causes and costs · frequently asked questions · directions

Do you recognise any of these symptoms?

You often notice an alternator that is not charging properly from one or more of these signs:

  • The red battery warning light is on while you drive
  • The lights get dimmer
  • The wipers and the fan work more slowly
  • The car does not start after a trip
  • You hear a squealing or humming sound from the engine
  • The battery keeps going flat, even when it is new

Is the battery warning light on and is the temperature gauge rising too? Then stop in a safe place and switch off the engine. In some cars the same belt also drives the water pump and sometimes the power steering. Call your breakdown service and read what to do if you have a breakdown.

How the alternator works

The alternator sits on the engine and is driven by a belt. As soon as the engine runs, the alternator generates electricity. It uses it to charge the battery and to power the lights, the wipers and the other electrical parts.

If the alternator stops charging, the car runs on the power from the battery. The battery slowly goes flat. First the electrical parts work less well. Then the engine cuts out or will not start again.

If the belt is the cause, the repair is often small. According to the ANWB, that is the best outcome you can hope for. That is why we measure first, before we replace anything.

What we do when the battery warning light is on

  • Measure the alternator’s charging voltage
  • Test the battery under load
  • Check the belt and the belt tensioner
  • Repair or replace the alternator in our own workshop
  • Look for anything that keeps drawing power when the car is switched off
  • Read the charging system data on a hybrid or electric car

Extra work is only done with your approval.

Battery warning light on: symptom, cause and solution

This table shows which symptom often goes with which cause. We only know what is really going on once we have taken measurements.

Symptoms of an alternator that is not charging and possible causes
Symptom Possible cause What we do
The red battery warning light comes on while you drive The alternator is not charging, or the belt that drives the alternator is slack or broken Measure the charging voltage and check the belt
Battery warning light on and the temperature gauge rising In some cars the same belt also drives the water pump and sometimes the power steering Stop first and call your breakdown service. Then we check the belt and the water pump
Squealing sound from the engine, especially in the cold or when starting A slack or worn belt Check the belt and belt tensioner and replace them if needed
Lights get dimmer, wipers slow down The battery is no longer being charged Test the alternator and the battery
Car does not start after a trip The battery is flat because the alternator is not charging Charge and test the battery, then measure the alternator
Humming or whining sound from the belts A bearing in the alternator or the belt tensioner Check the bearings and the belt tensioner
Hybrid or electric car reports a problem with the 12-volt battery The 12-volt battery or the system that charges it Read the system data and test the 12-volt battery

Alternator repair in our own workshop

An alternator can fail because of wear, a broken diode or a broken voltage regulator. We repair alternators in our own workshop. We also repair and replace starter motors ourselves. If a repair does not make sense, we replace the alternator. You hear in advance what it costs.

What does an alternator cost?

According to the ANWB, replacing an alternator on an average car costs about € 400. The work takes from half an hour to sometimes five hours, depending on how easy the alternator is to reach. That is a guide and not a quote from us. You hear in advance what it costs for your car. We also check the belt that drives the alternator during a service.

We work on all makes and models, including hybrid and electric cars. You are also welcome with a van or motorhome up to 3,500 kg. Our mechanics hold the GMTO certificate (the Dutch qualification for working on high-voltage systems), so they can work on hybrid and electric cars.

Why we measure first

When the battery warning light comes on, many people first think of a new battery. But if the alternator is not charging, the new battery soon goes flat as well. That is why we first measure the charging voltage, test the battery and check the belt. Then you hear what is wrong, what it costs and how long it takes.

You get a warranty on our repairs. We tell you which warranty applies when we give you the quote. Do you hear the belt squealing or screeching? Read more about a car that makes noise. Does your car not start at all? Then read more about a car that will not start.

Frequently asked questions about the battery warning light and the alternator

No need to click. All the answers are already open below.

What does the battery warning light mean while driving?

The red battery warning light shows that the battery is no longer being charged. When you start the car, the light comes on briefly. That is normal. If it stays on or comes on while you drive, something is wrong according to the ANWB. Often the alternator or the belt that drives it is the cause. The car then runs on the power from the battery until it is flat.

Can I keep driving with the battery warning light on?

No. Drive a short distance at most, to a safe place or to the garage. How far you can still get depends on the battery. Preferably avoid the motorway and driving in the dark. Keep an eye on the temperature gauge. Switch off everything you do not need, such as the radio, the seat heating and the rear window heater. Is the temperature gauge rising or is the steering getting heavy? Then stop in a safe place and call your breakdown service. Only switch off the engine once you are safely stopped, because it may not start again afterwards.

How do I know whether it is the battery or the alternator?

If the battery warning light comes on while you drive, the alternator or the belt is usually the cause. If the car starts badly in the morning but no light comes on while you drive, the battery is more often the cause. You only know for sure after a measurement. We test the battery, measure what the alternator is charging and check the belt.

How much does a new alternator cost?

According to the ANWB, replacing an alternator on an average car costs about € 400. The work takes from half an hour to sometimes five hours, depending on the car. That is a guide and not a quote from us. Whether repair or replacement suits your car best, you hear after the check, with the price in advance.

Can an alternator be repaired?

Yes. Often it can. An alternator can fail because of worn parts, a broken diode or a broken voltage regulator. We repair that ourselves. If a repair does not make sense, we replace the alternator. You hear in advance what it costs.

Why does my engine squeal when I start it?

A squealing sound when starting or in the cold often comes from a slack or worn belt. That belt drives the alternator. If it slips, the alternator charges less. Have the belt checked, because a broken belt can mean the alternator stops charging altogether. Read more about other noises your car can make.

My battery is new but keeps going flat. How can that be?

Then the alternator may not be charging the battery properly. Something may also keep drawing power when the car is switched off. We measure the charging voltage and look for that kind of parasitic drain. Read more about testing and replacing the battery.

How is the 12-volt battery in a hybrid or electric car charged?

Electric cars and full hybrids do not have a separate alternator. In those cars a converter charges the 12-volt battery. A mild hybrid often has a starter generator on the belt. According to the ANWB, breakdowns of electric cars in 2025 were mainly caused by flat tyres and the 12-volt battery. Our mechanics hold the GMTO certificate (the Dutch qualification for working on high-voltage systems) for hybrid and electric cars.

Alternator testing in Rotterdam-IJsselmonde

You will find us at Boterdiep 11 (3077 AW) in Rotterdam-IJsselmonde, close to Stadion Feijenoord (De Kuip) and exit 24 Rotterdam-Feijenoord on the A16. The A15 is five minutes’ drive away. There is free parking outside if there is space. The Stadion Feijenoord tram stop (line 3) is close by.

We are also easy to reach from Barendrecht, Ridderkerk, Capelle aan den IJssel, Krimpen aan den IJssel, Hendrik-Ido-Ambacht and Zwijndrecht. Appointments are made by phone.

Plan your route to Boterdiep 11 or see our contact page.

Opening hours
Monday to Friday: 8.00 to 17.30
Saturday: 9.00 to 15.00
Sunday: closed
We are closed on Christmas Day, Boxing Day and New Year’s Day.

Is your battery warning light on?

Call us during opening hours with your registration number. You drop the car off Monday to Friday between 8.00 and 8.30 am, or on Saturday at 9.00 am. You will hear the cost in advance and we only start once you agree.

Our score: 4.8 / 5 from 235 reviews. Read what our customers say (in Dutch).

Also see our pages on car battery testing, a car that will not start, starter motor replacement, an engine warning light, breakdowns and car diagnostics (in Dutch).

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