Vehicle knowledge: truck structure, systems and equipment
This domain examines whether you understand the hardware you are legally responsible for checking, and can name the order and the numbers. Expect questions on the air brake system, the auxiliary brakes, ABS/EBS, the coupling and the daily walk-around.
Air brake system (trykluftbremsesystem)
- A compressor charges reservoirs through a pressure regulator; working pressure is roughly 8-10 bar, with the compressor cutting out near the top of that range.
- The service brake is split into two circuits. If one fails, the other still brakes, but you must stop and get it repaired.
- A red warning lamp and buzzer warn of low pressure at roughly 4.5-5.5 bar. Below that the spring brakes (fjederbremser) apply automatically, because they need air pressure to release.
- Drain condensate from the reservoirs daily. Water in the system can freeze and kill the brakes.
- Check the pushrod travel and the slack adjusters; long travel means the brake is out of adjustment.
ABS, EBS and auxiliary brakes
ABS stops wheels locking, EBS adds electronic control and fault memory. A lamp that stays on after the self-test means a fault. The exhaust brake and retarder are auxiliary brakes: they save the service brake on long descents but do not replace it. Euro VI engines use SCR with AdBlue; an empty AdBlue tank derates the engine.
Coupling and the daily check (dagligt eftersyn)
Fifth wheel and kingpin, locking jaw, release handle fully home and safety catch closed, red and yellow air lines correctly connected, electrical cables, landing legs wound up. After coupling, do the tug test: apply the trailer brake and pull gently against it to prove the lock. Then walk around tyres and pressures, tread depth of at least 1.6 mm, lights, load securement, mirrors and wipers.
Worked example. On a cold morning the pressure gauge sits at 4 bar and the warning buzzer sounds. The correct response is not to drive and build pressure by idling; you wait until the regulator has cut out and the warning has stopped, then check that pressure holds with the engine off. If pressure falls again or will not build, the vehicle is unroadworthy and stays parked.
Traps that cost marks
- Swapping the red and yellow lines, or assuming air pressure is irrelevant once the engine runs.
- Treating the retarder as a substitute for the service brake.
- Believing ABS shortens braking distance on gravel or snow - it does not.