2018 Fiat Dethleffs — MOT failures & pass rate
394 MOT tests on the 2018 Fiat Dethleffs are in this dataset, and 95.7% of them passed. All cars of a similar age fail 11.1% of the time, so this is 6.7pp better than the group it competes with. Failures cluster in lighting & signalling, visibility and emissions & environmental.
What the MOT record shows
No single area dominates — lighting & signalling (4.1%) and visibility (1.8%) are close, so failures are spread across several systems rather than one weak point.
At component level the recurring items are headlamp aim, wipers and washers — headlamp aim alone was recorded 7 times.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Lighting & signalling | 4.1% | 16 |
| 2 | Visibility | 1.8% | 7 |
| 3 | Emissions & environmental | 0.8% | 3 |
| 4 | Brakes | 0.5% | 2 |
| 5 | Tyres | 0.3% | 1 |
| 6 | Seat belts & restraints | 0.3% | 1 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Headlamp aim | 7 |
| 2 | Wipers | 6 |
| 3 | Washers | 4 |
| 4 | Malfunction indicator lamp | 3 |
| 5 | Position lamp | 3 |
| 6 | Side repeaters | 3 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 4.3% | 17 |
| 2 | Brakes | 1.5% | 6 |
| 3 | Lighting & signalling | 1.3% | 5 |
| 4 | Visibility | 0.8% | 3 |
| 5 | Suspension | 0.8% | 3 |
| 6 | Body, structure & corrosion | 0.5% | 2 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 361 | 4.4% |
| 30-60k | 33 | 3.0% |
Failure rate by age
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2021 | 77 | 5.2% |
| 2022 | 77 | 1.3% |
| 2023 | 81 | 2.5% |
| 2024 | 80 | 7.5% |
| 2025 | 79 | 5.1% |
What to check before buying a 2018 Dethleffs
The failure pattern for this year is specific enough to inspect against: lighting & signalling accounted for 4.1% of tests. Start there.
- Lighting & signalling (4.1% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (1.8% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
- Emissions & environmental (0.8% of tests): More common on older diesels (DPF/EGR) — can be expensive; check for warning lights and smoke. Typical repair: £100–£600.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2018 Fiat Dethleffss pass their MOT?
95.7% of the 394 2018 Fiat Dethleffs MOT tests in this dataset passed — a 4.3% fail rate.
What is the most common MOT failure on a 2018 Fiat Dethleffs?
Lighting & signalling, recorded in 4.1% of tests, followed by visibility (1.8%).
Does the 2018 Dethleffs get worse with mileage?
Its MOT fail rate rises from 4.4% in the 0-30k band to 3.0% in the 30-60k band.
Methodology & source. Based on 394 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-27. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.