Which Cars Have the Most Light Failures at MOT?

Light failures are one of the most common MOT defects, but some cars are dramatically worse than others. We analysed 2,533,041 MOT tests across 40 popular car models to identify which vehicles rack up the most lamp and lighting defects.

The results are stark. The worst offender, the Citroen Grand C4 Picasso from 2010, has a light defect rate of 46.95 per cent. That means nearly half of all MOT tests on this model flag at least one lighting issue. Compare that to the best performer, the 2019 Audi Q3, where the rate is just 0.99 per cent. You are 47 times more likely to face a light-related MOT problem with the Citroen than the Audi.

This is not just about bulb quality. The data reveals patterns tied to electrical architecture, bulb technology, and how certain manufacturers approach lamp unit design. French marques, particularly Citroen and Peugeot, dominate the worst performers list. German premium brands fill the best performers roster. We will explain why.

Worst Cars for This Defect

Best Cars for This Defect

Why Do French Cars Have Such High Light Failure Rates?

The data is unequivocal. Of the top 20 worst performers, 18 are French. Citroen occupies 11 positions, Peugeot takes six. The Citroen Berlingo appears seven times across different model years, with defect rates clustering between 38 and 42 per cent. This is not random variation. This is systematic.

Two factors explain this. First, Citroen and Peugeot models from this era share electrical architectures with known connector corrosion issues. The Berlingo, built as a commercial vehicle platform adapted for family use, was engineered for cost, not longevity. Lamp connectors corrode, earths fail, and the multiplex wiring systems develop faults. These are high-mileage vehicles, averaging around 9,000 miles per year, and most examples currently sit between 65,000 and 85,000 miles. At this point, corroded connectors become endemic.

Second, many of these vehicles use complex headlamp units with separate bulbs for dipped beam, main beam, daytime running lights, and indicators, all housed in units prone to condensation. When moisture enters, it accelerates bulb failure and corrosion. Replacement lamp units for these models can cost £150 to £300 per side, so owners often bodge repairs or leave non-critical bulbs inoperative until MOT time.

The Isuzu Rodeo, a rebadged version of the Chevrolet Colorado pickup, appears twice in the worst performers. This is a different problem: poor build quality and agricultural electrical components not suited to UK weather. At over 80,000 miles, which is typical for these vehicles, the entire lighting loom is usually compromised.

At What Mileage Do Light Defects Usually Appear?

The data provides a useful metric here. The 'earliest mileage' figure shows the median odometer reading when a light defect first appears on MOT records. For the worst performers, this typically sits between 65,000 and 90,000 miles. The Citroen Berlingo from 2011, for example, starts showing light defects at a median of 92,912 miles. The Peugeot 5008 from 2010 begins at 86,266 miles.

But mileage is not the whole story. Age matters more. A 2017 Citroen Berlingo with 70,714 miles already has a 41.96 per cent defect rate. That is only around seven years old at first MOT defect. Compare this to the 2019 Audi Q3, which has covered just 32,560 miles when defects appear, yet the defect rate is still under one per cent. The Audi is simply better engineered.

For used car buyers, this means you should be particularly cautious with French models over seven years old, regardless of mileage. A low-mileage 2015 Citroen Berlingo might look appealing, but the electrical gremlins are age-related. Check every single light function during inspection.

Are LED Headlights More Reliable Than Halogen?

The data suggests yes, but with caveats. The best performers are dominated by cars from 2018 onwards, when LED headlights became standard on premium models. The 2019 Audi Q3, 2021 Audi Q2, and 2018 Mercedes GLC all use LED technology and all have defect rates around 1.3 per cent. Compare this to older halogen-equipped cars like the 2010 Citroen C4, which sits at 41.24 per cent.

LED bulbs last far longer than halogen. A quality LED unit can run for 20,000 to 30,000 hours. A halogen H7 bulb might manage 500 hours. Over the life of a car, halogens will fail multiple times. LEDs should outlast the vehicle. This explains why newer cars perform better, but only if the manufacturer has implemented LED systems properly.

However, when LEDs do fail, repair costs are brutal. Many LED headlamp assemblies cannot have individual bulbs replaced. The entire unit must be changed. For a 2019 Audi Q3, that can be £800 to £1,200 per side at a dealer. Halogen bulbs cost £10. The tradeoff is reliability versus repair cost when things go wrong.

Xenon HID lights sit somewhere in the middle. They are more reliable than halogen but less so than LED. When xenon ballasts fail (which they do, usually around 80,000 to 100,000 miles), replacement costs £200 to £400. None of the worst performers use xenon. This technology appeared mainly on premium brands between 2005 and 2018, which are not represented in the bottom 20.

The shift to LED is reducing defect rates, but only on well-engineered cars. A cheap LED retrofit on a 2012 Citroen Berlingo will not save you. Quality matters far more than technology.

How Do the Best and Worst Compare Directly?

This table makes the gulf clear. The worst performers have defect rates 40 to 45 times higher than the best. Pass rates tell a similar story. The French models struggle to achieve 70 per cent overall pass rates, while the German and Japanese premium cars sit comfortably above 90 per cent. When you consider that MOT failure rates by brand show Citroen and Peugeot consistently at the bottom, this light defect data fits a broader pattern of poor reliability.

Why Do Some Cars Get Condensation in Their Headlights?

Condensation inside lamp units is a defect category that testers flag regularly, and certain cars are chronic sufferers. The Citroen Berlingo and Peugeot 5008 are notorious. The problem is poor sealing around the lamp unit and inadequate breather systems.

Modern headlights are not hermetically sealed. They have small breather vents to equalise pressure as the bulb heats and cools. When these vents fail or become blocked, moisture gets trapped inside. Once in, it cannot escape. The result is persistent fogging and water droplets inside the lens. This scatters the beam, reduces output, and fails the MOT.

Cheap aftermarket lamp units make this worse. Many owners of high-mileage Citroens and Peugeots replace broken headlights with budget units from online suppliers. These often have inferior seals and poor quality breather valves. Within months, condensation appears. Genuine Citroen or Peugeot lamp units are expensive (£200 to £350 each), so owners gamble on cheap replacements. This is why even relatively recent Berlingos, like the 2017 and 2018 models, still have defect rates over 41 per cent.

In contrast, premium manufacturers use better quality seals, improved breather systems, and more durable lens materials. The Lexus CT from 2017 has a defect rate of just 1.33 per cent. Lexus lamp units are well sealed and use materials that resist UV degradation. The same applies to Audi, Mercedes, and Volvo. You get what you pay for.

If you are inspecting a used car, look closely at the headlight lenses. Any sign of fogging or water droplets inside means a future MOT failure. Walk away or negotiate hard on price.

How Common Are Headlamp Alignment Failures?

Headlamp alignment is tested at every MOT using an optical beam setter. If the beam pattern is too high, too low, or points the wrong direction, it fails. This defect is common on cars that have had accident damage or cheap headlight replacements.

The data does not separate alignment failures from other light defects, but anecdotally, alignment issues are more prevalent on older cars with aftermarket lamp units. The Citroen Berlingo and Peugeot 5008, both common as commercial vehicles and frequently subject to minor knocks, suffer badly here. When a cheap replacement headlight is fitted without proper alignment adjustment, the beam pattern is often incorrect from day one.

Premium cars suffer less because owners are more likely to use main dealer repairs, where alignment is checked as standard. The 2019 Audi Q3 and 2018 Mercedes GLC have sophisticated self-levelling systems that adjust beam height automatically based on load. These systems rarely drift out of spec unless there is a serious electrical fault.

For buyers, this means you should test drive any used car at night on unlit roads. If the headlights seem weak or the beam pattern looks wrong, budget for a professional alignment check. This costs £30 to £50 at most garages and could save a future MOT failure.

What Are Typical Repair Costs for Light Defects?

Repair costs vary wildly depending on the fault and the car. A simple halogen bulb replacement costs £10 for the bulb and perhaps £20 labour if you cannot do it yourself. Many cars, particularly French models, have fiddly bulb access requiring bumper removal. This inflates labour to £50 to £80.

Corroded connectors and earth faults require electrical diagnosis. Expect £60 to £100 labour to trace and fix these issues. If the wiring loom is compromised, costs escalate. A full headlight loom replacement on a Citroen Berlingo can run to £200 to £300 including labour.

Condensation in lamp units usually means a new headlight. For a Peugeot 5008, budget £200 to £350 per side for genuine parts, or £80 to £150 for aftermarket units. As noted, cheap aftermarket lamps often fail again within a year, so you might end up paying twice.

For cars with LED or xenon systems, the numbers jump. A xenon ballast replacement costs £200 to £400. A full LED headlight unit on an Audi Q3 can be £800 to £1,200. If your car is out of warranty and you face this bill, it hurts.

The best approach is to catch issues early. If you notice a bulb out or dimming, replace it immediately. Waiting until MOT time often means multiple defects have accumulated. Regular checks cost nothing and could prevent a hefty repair bill. According to the AA, around 15 per cent of UK drivers have at least one defective light at any given time, usually without realising it.

Which Model Years Should You Avoid?

Avoid any Citroen Berlingo, Citroen Grand C4 Picasso, or Peugeot 5008 from 2010 to 2018. The data is consistent across all these model years. Defect rates sit between 38 and 47 per cent. These are fundamentally flawed vehicles from a lighting reliability perspective.

The 2010 to 2012 Peugeot 3008 and 207 also perform poorly. If you are considering a budget family MPV or SUV, steer clear of these French offerings unless you enjoy MOT failures and electrical repair bills.

The Isuzu Rodeo from 2010 and 2011 should also be avoided. These are niche vehicles, but if you encounter one, the light defect rates are appalling. At nearly 44 per cent, you are almost certain to face problems.

In contrast, anything from 2018 onwards with LED headlights from Audi, Mercedes, Lexus, or Volvo is a safe bet. The defect rates are negligible. Even the Tesla Model 3 from 2021, which has mixed reviews overall (as seen in our overall reliability rankings), manages a light defect rate of just 1.46 per cent. Build quality might be questionable, but the lighting systems work.

What Should You Check When Buying a Used Car?

Before handing over money for any used car, check every single light function. This means headlights (dipped and main beam), fog lights, brake lights, reversing lights, number plate lights, and all indicators. It takes five minutes and could save hundreds of pounds.

Look inside the headlight lenses for condensation, fogging, or water droplets. If you see any moisture, the lamp unit seals have failed. This is a guaranteed future MOT defect and a strong negotiating point.

Check lens clarity. Yellowed or clouded lenses scatter light and reduce output. UV degradation causes this on older cars. Aftermarket lens restoration kits exist, but they are temporary fixes. Budget for replacement lamps if the lenses are badly degraded.

Test the lights at night if possible. Drive on an unlit road and check the beam pattern. If the lights seem weak or the pattern looks odd, alignment is off. This is an MOT fail and a sign of previous accident damage or poor repairs.

If you are buying a French model from 2010 to 2018, assume you will face light defects within the first year of ownership. Factor this into your offer price. A £3,000 Citroen Berlingo might need £300 to £500 spent on lighting repairs before the next MOT. That changes the value equation.

For premium cars with LED or xenon systems, verify that all functions work. Replacement costs are huge if something fails post-purchase. If a dealer refuses to demonstrate all lights working, walk away.

You can also check the car's full MOT history for free at gov.uk/check-mot-history. Look for recurring light defects in previous tests. If the same issue appears multiple times, it has not been fixed properly.

Frequently Asked Questions

Light failures might seem like minor issues, but they are reliable indicators of broader electrical and build quality problems. The data makes clear that French marques from 2010 to 2018 are deeply flawed in this area, while premium brands from 2018 onwards have largely solved the problem with LED technology.

If you are buying used, avoid the worst performers entirely. A cheap Citroen Berlingo will cost you dearly in repairs. If you must buy French, factor in £300 to £500 for lighting repairs within the first year. Better still, choose a 2018 or newer premium car with LEDs and enjoy near-zero defect rates.

Check any car's full MOT history before you buy. PlateInsight gives you instant access to all MOT records, including specific defect details, so you can see exactly what has failed in the past. We offer 5 free vehicle checks to get you started. Make an informed decision based on real data, not guesswork.