Heavy Vehicle Mechanic (Craft Apprenticeship Curriculum)
The Heavy Vehicle Mechanic craft apprenticeship curriculum tests the knowledge a commercial-vehicle technician needs in Irish workshops: chassis and driveline systems, air brakes, steering and suspension, 24 V electrical/electronic systems, hydraulics, engine principles, diagnostics and roadworthiness. Questions are practical, so link every answer to a safe procedure, a measured value or a manufacturer’s specification.
Core rules and systems
- Before work under a vehicle, chock the wheels, support it on rated stands and isolate the 24 V batteries. Drain air reservoirs before opening brake circuits.
- Use the manufacturer’s torque figures and tightening sequences; a calibrated torque wrench is part of the repair, not an accessory.
- Air-brake diagnosis checks compressor build-up, governor cut-out, leak-down and air-dryer function. A pressure warning or slow build-up is a defect, not a nuisance.
- Electrical tests use loaded voltage-drop measurements, not open-circuit voltage alone. A 24 V circuit can show 24 V at rest and fail under load.
- Follow a diagnostic sequence: verify the complaint, gather fault codes and live data, test the suspected circuit, repair, then confirm the repair under operating conditions.
Worked example: engine displacement
A six-cylinder diesel has a bore of 120 mm and a stroke of 155 mm. Convert to centimetres: 12.0 cm and 15.5 cm. Swept volume per cylinder = π/4 × bore² × stroke = 0.7854 × 144 × 15.5 = 1,753 cm³, or 1.753 L. For six cylinders: 1.753 × 6 = 10.52 L. The reasoning matters: displacement is a geometric engine size, not a direct power rating; it is used with boost pressure, fuel delivery and speed when assessing performance.
Traps that cost marks
- Mixing kerb weight, GVW and design gross vehicle weight when answering load or brake questions.
- Replacing parts because a fault code points to a sensor, instead of testing the circuit and mechanical condition first.
- Reusing torque-to-yield fasteners or skipping a specified sequence.
- Treating air-brake pressure loss as normal; roadworthiness and CVRT standards treat it as a defect.
- Forgetting that tachograph and CVRT compliance affect the mechanic’s documentation and test preparation.