HVAC is a mechanic’s term for your car’s ventilation system. The letters stand for Heating, Ventilation, and Air-Conditioning.

The hydraulic circuit is a closed system of tubes that contain hydraulic fluid. When pressure is applied at one end of the hydraulic circuit, it travels through the tubes to the other end.

A generator is like an alternator in that it generates electrical current to both keep the battery charged and supply electricity for a vehicle’s electric system.

Glazing is a shiny coating on the inside surface of a fan, or serpentine belt. Glazing occurs when the belt slips repeatedly at a high speed. It is a sign that the belt needs replacement.

Glow plugs are only found on vehicles with diesel engines. Glow plugs heat up the diesel fuel before the engine has been started, making the engine easier to start.

The hazard relay controls the flashing of the hazard warning lights.

An acronym for Hydrocarbons. Any number of compounds of carbon and hydrogen used as fuel, such as gasoline. High levels of hydrocarbons in tailpipe emissions are a result of unburned gasoline.

The head gasket seals the cylinder head to the engine block. It is subject to tremendous pressures, and often fails if and when an engine overheats.

The heater core is a miniature radiator that sits in the dashboard. When the heater is turned on, it opens the heater valve which lets hot coolant into the heater core, which then warms the air coming into the vehicle’s

The heater ducts are the tubes that connect the heater fan to the vents in your vehicle’s dashboard.

The heater fan is the interior fan that controls the speed of air being introduced into the interior.

This is a general term that refers to a gasoline’s general quality – for instance, its octane rating and package of additives. The two common terms for gas grades are “regular” for low-grade gas, and “premium” for high-grade gas.

A gasket is a piece of material that seals two parts together. The gasket prevents air or fluids from leaking between the parts.

A gauge is a type of instrument that measures or displays levels of a certain system. For instance, the gas gauge in your car measures the fuel level, while the temperature gauge measures the engine temperature.

The gear selector is the lever that lets you select a certain gear with an automatic transmission. In modern cars, the gear selector is often connected to the brake pedal, so that you can only shift into drive or reverse

Gear synchronizers allow you to upshift and downshift a manual transmission without grinding gears. They do this by synchronizing, or matching, the speed of the engine and the speed of the gear you are selecting. If your car didn’t have

The gearshift lever is the lever that lets you select gears with a manual transmission.

This is a series of rods and/or cables that connect the gearshift lever or gear selector to the transmission.

Fuel injection is a system by which fuel is directly sprayed into the intake manifold or intake port at high pressure. Fuel injection is often controlled by a computer, allowing precise monitoring of efficiency and performance by the car’s computer.

A fuel injector is a nozzle that sprays fuel into the intake manifold or intake port.