Trade Safety, Tools, Measuring Instruments and Workshop Practice
What the exam tests
This domain checks whether you can work on vehicle electrical systems without injuring yourself or damaging test equipment. Expect questions on battery handling, insulated tools, multimeter connections, torque and workshop control.
Core rules
- Remove rings, watches and metal jewellery before touching a battery or starter cable. A short through a ring can cause severe burns.
- Treat lead-acid batteries as both chemical and explosive hazards: charge in a ventilated area, no sparks, and neutralise acid spills with bicarbonate of soda.
- Disconnect the negative terminal first and reconnect it last, so a spanner touching the body does not complete the circuit.
- Use a high-impedance digital multimeter (typically 10 MΩ) for electronic circuits. A low-impedance test light can destroy a 5 V reference or an ECU driver.
- Volts are measured in parallel; current in series; resistance with the circuit dead and isolated. Select the range before connecting.
- Torque battery terminals and clamp bolts to specification. Overtightening distorts posts and causes hidden high-resistance joints.
Worked example
A car has a flat battery overnight. Set the meter to DC current, 10 A range, and connect it in series between the negative post and the disconnected negative cable. Close all doors, wait for modules to sleep (often 20–40 minutes), then read. A typical specification is below 50 mA. If you see 350 mA, remove fuses one at a time and watch the reading; the fuse that drops the current to normal identifies the circuit. Do not pull the fuse before the modules sleep, or you will measure normal wake-up current and chase a false fault.
Traps
Using the current range to measure voltage blows the meter fuse. Testing resistance on a live circuit gives meaningless readings. Piercing insulation creates corrosion paths. Do not use a test light on airbag circuits.