- H -

Hazard System

A driver-controlled system of flashing front-and rear-marker lights to warn approaching motorists of a potential hazard.

Hazardous Material

Any material that can cause illness, injury, or death or pollute the air , ground, or water.

Hazardous Waste

1. Any product used in a system that is considered harmful to people and/or the environment. 2. Any poisonous substance, the byproduct of a poisonous substance, or one that contains carcinogens and is considered unsafe for animal or plant life b the EPA.

HBV

Heater blower voltage.

HC

An acronym for hydrocarbon. 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.

HC-CO Meter

A device using an infrared sensor to measure the amount of hydrocarbons, in parts per million and carbon monoxide, in percent, in the vehicle exhaust.

HCB

Heated crankcase breather.

HCV

Heat control valve.

HD

An acronym for heavy duty.

HDB

Heavy duty braided.

HDC

Heavy duty cooling.

HDC-CTO

Heavy duty cooling coolant temperature override.

HDMA

An acronym for Heavy Duty Manufacturers Association.

HDRA

1. An acronym for Heavy Duty Representatives Association. 2. An acronym for High Desert Racing Association.

HDT

Heavy duty thermoplastic.

HDV

Heavy duty vehicle.

He

Helium An element with the atomic number of 2.

Head

1. That part of an engine that covers the top of the cylinders and pistons and usually contains the combustion chambers and valve train. 2. That part of a compressor that covers the valve plates and separates the high side from the low side of an air-conditioning system.

Head Bolts

The bolts that fasten the cylinder heads to the engine block.

Head Gasket

A gasket used to seal the cylinder head to the engine block.