ASE B5 Mechanical & Electrical Components key terms

A temperature-controlled valve in the engine coolant circuit that opens and closes to regulate coolant flow, helping the engine reach and maintain its designed operating temperature.

A heat exchanger mounted at the front of the vehicle that transfers heat from engine coolant to outside air, lowering coolant temperature before it returns to the engine.

An engine-driven or electric pump that circulates coolant through the engine block, radiator, and heater core so heat can be carried away and the engine stays within its normal temperature range.

A liquid mixture of water and antifreeze additives that absorbs heat from engine parts and releases it through the radiator, while also raising the boiling point and lowering the freezing point.

A spring-loaded cap that seals the cooling system and holds it under pressure, raising the coolant boiling point; it also releases pressure to the recovery tank when expansion occurs.

A rechargeable lead-acid storage battery that supplies electrical energy for starting, lighting, and electronics when the engine is off and acts as a voltage stabilizer when the charging system runs.

An engine-driven generator that produces alternating current, rectifies it to direct current, and charges the battery while powering the vehicle's electrical loads when the engine is running.

A high-torque electric motor that engages the engine flywheel or flexplate and cranks the engine until it starts, drawing heavy current from the battery through a solenoid or relay.

A push-in electrical protection device with a metal strip that melts when current exceeds its rating, opening the circuit to prevent wiring damage or fire.

An electrically controlled switch that uses a small current through a coil to close or open contacts carrying a larger current, commonly used to control fans, pumps, and lights.

A return path for electrical current created by connecting a circuit to the vehicle's metal body or frame, which serves as a common conductor back to the battery negative terminal.

A hydraulic pump driven by the brake pedal that pressurizes brake fluid and sends it through brake lines to the wheel brakes, creating the force needed to slow or stop the vehicle.

A hydraulic assembly that clamps brake pads against a spinning brake rotor when pressurized fluid enters it, converting hydraulic pressure into friction that slows the wheel.

A friction material bonded to a steel backing plate that presses against a brake rotor to create stopping friction; pads wear over time and must be replaced before the backing plate damages the rotor.

A cast-iron or composite disc that rotates with the wheel and provides the friction surface for brake pads; it also helps dissipate heat generated during braking.

A hygroscopic hydraulic liquid, usually glycol-based, that transmits pressure from the master cylinder to the wheel brakes; it must resist boiling and cannot be compressed under normal operating conditions.

A sensor at each wheel that reports wheel rotation speed to the anti-lock brake system, allowing the system to detect wheel lockup and modulate brake pressure to preserve steering control.

A steering mechanism that converts rotation of the steering wheel into sideways movement of a toothed rack, pushing or pulling tie rods to turn the front wheels.

A link that connects the steering rack or steering arm to the steering knuckle, transmitting steering force to the wheel while allowing suspension movement through a ball-and-socket joint.

A pivoting joint with a ball stud inside a socket that connects a control arm to a steering knuckle, allowing the suspension to move up and down while the wheel steers.

A suspension assembly combining a coil spring, shock absorber, and structural strut housing into one unit that supports the vehicle's weight and locates the wheel.

Adjustment of the angles at which wheels meet the road, primarily camber, caster, and toe, so tires wear evenly and the vehicle tracks straight with minimal steering effort.

A belt-driven or electric pump that compresses refrigerant vapor and circulates it through the air-conditioning system, raising its pressure and temperature so heat can be released.

An air-cooled heat exchanger mounted in front of the radiator that receives hot, high-pressure refrigerant vapor from the compressor and releases heat so the refrigerant condenses into a liquid.

A heat exchanger inside the passenger compartment where low-pressure refrigerant absorbs heat from air passing through it, cooling the air while the refrigerant vaporizes.

A fluid with a low boiling point that circulates through an air-conditioning system, absorbing heat as it evaporates and releasing heat as it condenses under pressure.

A small radiator-like heat exchanger inside the HVAC case that uses hot engine coolant to warm air blown into the passenger compartment.

A small electric motor that moves a door inside the HVAC case to mix heated and cooled air, allowing the driver or climate control system to set the desired cabin temperature.

A single, flat, ribbed belt that drives multiple engine accessories such as the alternator, water pump, power steering pump, and air-conditioning compressor from the crankshaft pulley.

A threaded electrical device that screws into the cylinder head and creates a spark across its electrodes to ignite the compressed air-fuel mixture in a gasoline engine.

A transformer that steps up low battery voltage to the high voltage needed to jump the spark plug gap and ignite the air-fuel mixture in the combustion chamber.

An electrically controlled valve that sprays a precise amount of pressurized fuel into an engine's intake port or cylinder, where it mixes with air for combustion.

A fluid coupling between an engine and an automatic transmission that multiplies torque at low speeds and allows the engine to idle while the vehicle is stopped.

A constant-velocity driveshaft with flexible joints at each end that transmits power from the transaxle to a driven wheel while allowing the suspension to move and the wheel to steer.

An assembly containing an inflator, a folded airbag, and a cover, mounted in the steering wheel, dashboard, seat, or roof rail to deploy during a significant collision and cushion occupants.

A coiled ribbon cable inside the steering column that maintains electrical continuity for the driver airbag, horn, and steering wheel controls while the wheel rotates.

A pyrotechnic or spring-loaded device that retracts the seat belt slightly at the moment of a crash, removing slack and holding the occupant firmly in the seat before the main belt load limiter acts.

A sensor that detects sudden deceleration or acceleration caused by a collision and sends a signal to the SRS control module, which decides whether to deploy airbags and pretensioners.

The computer that monitors crash sensors and system readiness, then triggers airbag inflators and seat belt pretensioners in a deployment event while storing diagnostic trouble codes.