Common problems

Mercedes-Benz M-Class electrical and lighting problems

How often MOT testers find lights and electrics faults on the Mercedes-Benz M-Class at each age, against all cars of the same age, and which items come up most. From 139,242 DVSA MOT tests taken 2022 to 2025.

MOT data updated 28 September 2026

At 10 years, the most tested age

Lights and electrics fails per 100 MOTs (n=14,152)4.9

All cars at 10 years (n=9,049,507)11.2

Lights and electrics advisories and minor defects per 100 MOTs (n=14,152)2.3

All cars, same age (n=9,049,507)5.9

What stands out

At 10 years, 4.9 of every 100 MOTs of the Mercedes-Benz M-Class found a lights and electrics fail (n=14,152), against 11.2 for all cars of that age (n=9,049,507).
It is above the all-car rate at 5 of the 18 ages with at least 1,000 tests.
The gap is widest at 11 years: 6.4 per 100 MOTs against 13.3 for all cars.
The lights and electrics fail item recorded most often at 10 years: dipped headlight not working, on 1.0 per 100 MOTs.
The most common lights and electrics advisory or minor defect: position lamp: with a multiple light source up to 1/2 not functioning, on 0.8 per 100 MOTs.

Lights and electrics fails by age

Solid line: this model. Dashed line: all cars at the same age.

Mercedes-Benz M-Class: lights and electrics fails and advisories per 100 MOTs, by age, against all cars. Ages with fewer than 1,000 tests are not shown.
Age	Tests (n)	Fails	All cars	Advisories	All cars
7 years	3,282	2.8	5.8	0.6	2.5
8 years	7,249	3.7	7.3	1.2	3.4
9 years	11,539	4.3	9.2	1.8	4.5
10 years	14,152	4.9	11.2	2.3	5.9
11 years	13,780	6.4	13.3	3.7	7.5
12 years	12,787	9.6	15.4	5.3	9.3
13 years	10,695	12.7	17.0	8.8	10.8
14 years	10,487	15.8	18.3	11.0	12.2
15 years	10,203	16.9	19.5	11.3	13.7
16 years	9,416	16.3	20.4	12.6	15.3
17 years	8,031	17.1	21.0	14.9	16.9
18 years	6,935	19.7	21.4	19.0	17.8
19 years	5,786	21.5	21.5	22.7	17.9
20 years	4,860	23.7	21.2	25.2	17.4
21 years	3,963	24.0	20.6	25.2	16.7
22 years	2,955	21.7	19.7	25.8	15.5
23 years	2,031	21.9	18.6	23.5	14.2
24 years	1,091	22.9	17.2	25.8	12.5

Lights and electrics fail items at 10 years

Lights and electrics fail items on the Mercedes-Benz M-Class at 10 years (n=14,152), per 100 MOTs, with all cars at the same age (n=9,049,507).
Item	Per 100 MOTs	All cars	Typical repair (estimate)
Dipped headlight not working	1.0	1.7	£18 to £86 per lamp
Headlight aimed too high	0.9	0.8	£16 to £39 per car (rough guide)
Brake light not working	0.8	2.0	£10 to £47 per lamp
Headlamp aim: too low	0.6	1.2	£16 to £39 per car (rough guide)
Rear fog lamp: not working	0.3	0.4	£10 to £47 per lamp
Side/position light not working	0.3	2.4	£10 to £47 per lamp

Lights and electrics advisories and minor defects at 10 years

Advisories and minor defects are recorded, but the car still passes. Across all cars, a part with an advisory or minor defect failed at the next MOT 5.5 times in 100 (n=88,666,940 pairs of consecutive MOTs), against 0.3 times in 100 when the same part had none (n=12,936,860,350).

Lights and electrics advisories and minor defects on the Mercedes-Benz M-Class at 10 years (n=14,152), per 100 MOTs, with all cars at the same age (n=9,049,507).
Item	Per 100 MOTs	All cars
Position lamp: with a multiple light source up to 1/2 not functioning	0.8	0.3
Rear reflectors: defective or damaged by up to 50% of the reflecting surface	0.4	0.2
Registration plate lamp(s): inoperative in the case of multiple lamps or light sources	0.4	3.2

Repair estimates are a guide for an independent garage: labour at the national median local garage rate (median £78 an hour from 65 garages, ONS price quotes) times estimated labour hours, plus a parts band. Labour hours and most parts bands are estimates, not quotes, and prices vary by model, engine and region. A warning light fault shows the cost of the diagnosis only.

What to check on a viewing

On the Mercedes-Benz M-Class, the lights and electrics items testers fail most are dipped headlight not working; headlight aimed too high; brake light not working.

With someone outside, try every light: dipped and main beam, indicators, brake lights, fog lights and number plate lamps.
Check that the warning lights come on with the ignition and go out once the engine runs.
Look for misted, cracked or yellowed headlamp lenses.

Ask for the car's MOT history: a lights and electrics advisory that repeats from year to year has not been fixed. GOV.UK MOT history.

Questions

What are the common electrical and lighting problems on the Mercedes-Benz M-Class?

At 10 years (14,152 MOTs), the lights and electrics fail items testers record most often are dipped headlight not working (1.0 per 100 MOTs), headlight aimed too high (0.9 per 100 MOTs), brake light not working (0.8 per 100 MOTs). The most common lights and electrics advisories or minor defects are position lamp: with a multiple light source up to 1/2 not functioning (0.8) and rear reflectors: defective or damaged by up to 50% of the reflecting surface (0.4).

Does the Mercedes-Benz M-Class have more electrical and lighting problems than other cars?

At 10 years it has 4.9 lights and electrics fails per 100 MOTs against 11.2 for all cars of the same age (6.3 fewer). It is above the all-car rate at 5 of the 18 ages with enough tests.

What does a lights and electrics repair cost on the Mercedes-Benz M-Class?

For dipped headlight not working, an independent garage estimate is £18 to £86 per lamp. This is a guide built from the national median garage labour rate and estimated labour hours, not a quote.

Electrical and lighting problems on other Mercedes-Benz models

Read this with care. A fail rate is not a measure of build quality. How far cars are driven, how they are used and how well owners maintain them all change it, and wear items such as tyres and brake pads are common fails. Compare a model only with cars of the same age. Methodology and limits.

The all cars figures cover all class 4 vehicles (cars and light vans) tested at the same age.

Looking at a Mercedes-Benz M-Class?

These figures describe the model, not the car in front of you. Found one you might buy? See what the VetTheCar Buying Report covers, or use the tools that work without a registration.

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Repair estimates: ONS consumer price quotes for local garage labour (09/2025 to 08/2026), the MOT inspection manual for defect wording, and estimated labour hours and parts bands. Not affiliated with or endorsed by ONS.

Source

Contains public sector information licensed under the Open Government Licence v3.0. Source: DVSA anonymised MOT test data, class 4 normal MOT tests, 2022 to 2025. MOT data updated 28 September 2026.

Not affiliated with or endorsed by DVSA. How we calculate these figures · Data sources