Vehicle technology: maintenance, tyres, brakes and lighting
This domain tests the daily technical checks you are expected to perform and understand: tyres, brakes including the trailer's overrun system, lighting and connectors, and the walk-around inspection that keeps the combination legal.
Tyres
- Minimum tread depth is 1.6 mm for cars and minibuses; check across the full width and around the circumference, not just one groove.
- Load index and speed rating must match what the vehicle needs, and pressure must be set cold to the manufacturer's figures - higher when fully loaded.
- Trailer tyres are the neglected ones: check age (DOT code), perishing, cracks and pressure. A trailer standing for months loses pressure quietly.
- Denmark has no mandatory winter tyre period, but the vehicle must be suited to the conditions; in ice and snow that in practice means winter or all-season tyres with adequate tread.
Brakes
- Trailers over 750 kg must be braked; up to 3,500 kg they normally use an overrun brake with a breakaway cable.
- Test after coupling: move slowly and apply the brakes - the trailer should brake without snatching - and check the trailer handbrake holds on a slope.
- Watch pad wear, brake fluid level and the ABS/EBS warning lamps. On long descents, use engine braking to avoid fade.
Lighting and connectors
- Check every light with a helper: position, dipped, main beam, indicators, brake, reversing, rear fog and number-plate lamp.
- The 13-pin connector is the most common trailer fault - corroded pins and a bad earth cause bizarre symptoms such as one indicator working and another glowing faintly. Clean with contact spray and check the earth return.
- Re-aim headlamps when heavily loaded; rear fog lights only in seriously reduced visibility.
Daily walk-around
- Oil, coolant, washer fluid, wipers, mirrors, doors and emergency exits, extinguisher, first-aid kit, warning triangle, and the spare wheel or repair kit.
Worked example
The trailer's brake lights work but the left indicator does not, and the bulb looks intact. Reasoning: a corroded pin or a failing earth in the 13-pin plug makes the current find another path through the other bulbs. You may not drive - an inoperative indicator is a defect you can be fined for and it is genuinely dangerous. Clean or repair the plug and re-test with a helper before departure.
Traps that cost marks
- Checking lights alone and assuming the trailer is fine.
- Ignoring trailer tyre age because the tread looks deep.
- Over-inflating "for economy" and losing grip.
- Believing ABS shortens braking distance on ice.