Cert III Auto Electrical flashcards
Cert III Auto Electrical · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Ohm's law
- Voltage equals current multiplied by resistance, expressed as V = I × R. It links the three basic electrical quantities and allows any one to be calculated when the other two are known.
- Electrical power formula
- Power in watts equals voltage multiplied by current, and can also be written as current squared times resistance or voltage squared divided by resistance.
- Series circuit current
- In a series circuit the same current flows through every component, total resistance is the sum of individual resistances, and supply voltage divides across the loads.
- Parallel circuit voltage
- In a parallel circuit the voltage across each branch is the same, total resistance is less than the smallest branch resistance, and branch currents add to the total.
- Voltage drop under load
- The difference between supply voltage and the voltage reaching a load while current flows. Testing under load, not open circuit, reveals high-resistance cables or connections.
- Insulation resistance test
- A test using a megohmmeter that applies a high test voltage to check whether insulation between a conductor and earth has broken down. Low readings indicate a fault.
- Ammeter connection
- An ammeter must be connected in series with the circuit so the current being measured passes through it. Connecting it across a supply causes a short circuit.
- Voltmeter connection
- A voltmeter is connected in parallel with the component or circuit section being tested, because it measures the potential difference between two points.
- Battery earth lead removal
- Disconnecting the negative, earth-side battery lead first reduces the risk of a short circuit through tools. Reconnect it last after completing the work.
- Cold cranking amps
- A rating of the current a battery can deliver at a specified cold temperature for a set time while maintaining a minimum voltage. It indicates starting capability, not reserve capacity.
- Reserve capacity
- The time in minutes a fully charged battery can supply a specified current at a stated temperature while staying above a minimum voltage, indicating ability to support loads if charging fails.
- Fuse rating purpose
- A fuse is selected to protect the conductor and circuit from excessive current. It should be rated below the cable's current capacity but above normal circuit load.
- Continuity test
- A test confirming a low-resistance path exists between two points. It is performed with the circuit de-energised and the component isolated to avoid false readings.
- Multimeter function selection
- Choosing the correct meter mode and range before connecting probes prevents incorrect readings and meter damage, such as measuring voltage while set to resistance.
- Alternator field control
- The regulator varies current through the rotor field winding to control magnetic strength and therefore alternator output, keeping charging voltage within a set range.
- Charging voltage check
- With the engine running and electrical loads off, a 12 V system should show roughly 13.5 to 14.5 volts at the battery. Outside this range indicates a charging fault.
- Alternator belt slip symptom
- A slipping drive belt can cause intermittent or low charging output, often with noise, and may show a glazed or worn belt surface on inspection.
- Starter motor current draw
- A starter draws a high current during cranking. Excessive draw with slow cranking suggests internal starter faults or high mechanical resistance in the engine.
- Starter solenoid function
- The solenoid engages the starter drive with the flywheel ring gear and closes a heavy-duty contact to supply current to the starter motor windings.
- Cranking voltage drop
- Measuring voltage at the battery and at the starter during cranking shows cable and connection losses. A large difference indicates excessive resistance in the circuit.
- Relay coil and contacts
- A relay uses a low-current coil to operate higher-current contacts. A clicking relay can still have burnt contacts, so output must be tested, not just the click.
- Relay terminal identification
- Relay pins are identified by function: coil supply and coil earth operate the relay, while contact pins switch the load circuit. Wiring diagrams confirm pin numbering.
- Headlight high current circuit
- Headlamps often use a relay because switch contacts cannot carry lamp current directly. The switch controls the relay coil and the relay contacts feed the lamps.
- Shared earth fault effect
- Several lamps or accessories may share an earth point. Corrosion or looseness there can cause dim lights or operation of unrelated circuits through back-feeding.
- CAN bus termination
- A controller area network bus has terminating resistors at each end, typically around 120 ohms each. Incorrect termination or wiring faults disrupt communication between modules.
- Controller area network purpose
- A serial data network allowing electronic control modules to exchange information over shared wiring, reducing the number of individual conductors needed between components.
- Fusing accessory circuits
- Accessory circuits require a fuse at the supply end of the conductor, so any short downstream is interrupted before the cable overheats or catches fire.
- Trailer lighting wiring
- Trailer plugs use defined pin assignments for stop, tail, turn and earth circuits. Incorrect pin wiring or a poor earth causes cross-feeding between lamps.
- Glow plug function
- Glow plugs heat the combustion chamber in a diesel engine to assist cold starting. They are controlled by a timer or module and draw significant current.
- Horn circuit components
- A horn circuit typically includes a fuse, relay, horn switch and earth path. Testing each point determines whether the fault is supply, control or the horn unit.
- Wiper motor park position
- Wiper motors use a park switch to keep the motor powered until the blades reach the rest position after the switch is turned off.
- Instrument cluster sender signal
- Sensors such as temperature and fuel level send a variable resistance or voltage signal to the cluster. Incorrect readings may come from the sender, wiring or earth.