Automotive Heating & Cooling Systems Study Guide Flashcards

These flashcards cover key concepts, components, and functions related to automotive heating and cooling systems to assist in exam preparation.

R-134a

A refrigerant commonly used in modern automotive A/C systems.

Condenser

A component that dissipates heat from the refrigerant.

Expansion valve

The device that separates the high-pressure and low-pressure sides of the A/C system.

Evaporator

The component where refrigerant absorbs heat and evaporates.

Receiver-drier

Stores refrigerant and removes moisture in the A/C system.

PAG oil

The type of oil used with R-134a refrigerant.

Manifold gauge set

A tool used to measure A/C system pressures.

Restricted condenser

A common issue indicated by high pressure on both sides of the A/C system.

Low refrigerant charge

Usually indicated by low pressure on both sides of the A/C system.

Safety goggles and gloves

Required safety equipment when working with refrigerant.

Heater core

Functions as a liquid-to-air heat exchanger.

Stuck-open thermostat

Causes the engine to run too cool.

Stuck-closed thermostat

Causes the engine to overheat.

Resistor pack

Controls blower motor speed in older vehicles.

In-car temperature sensor

Monitors cabin temperature in automatic climate control.

Blend door

Mixes heated and cooled air for desired cabin temperature.

Superheat

The temperature of vapor refrigerant above boiling point at low side pressure.

Subcooling

The temperature of liquid refrigerant below its condensation temperature at high side pressure.

Low-pressure cutout switch

Prevents compressor damage during low-pressure conditions.

High-pressure cutout switch

Prevents compressor damage during excessively high pressure.

Accumulator

Maintains system pressure on the low side in an orifice tube system.

Vacuuming the system

Removes air and moisture from the A/C system before charging.

Cooling fan not working

Can cause poor A/C cooling at idle.

Water pump

Circulates coolant through the engine and radiator.

Cavitation

Formation of vapor bubbles in a water pump due to low pressure.

Radiator cap

Maintains system pressure and raises the boiling point of coolant.

50/50 antifreeze and water

Typical coolant mixture ratio.

Heat soak

When the engine retains heat after shutdown.

Heater core leak

Indicated by a sweet smell inside the cabin.

UV dye

Used to detect refrigerant leaks.

Compressor

Pumps refrigerant and increases its pressure in an A/C system.

Flexible A/C hoses

Absorb vibration and allow engine movement.

Ambient temperature sensor

Prevents A/C from operating in freezing conditions.

Radiator

Most responsible for removing engine heat.

Thermostat bypass

Allows coolant to circulate when the thermostat is closed.

Heater control valve

Regulates coolant flow through the heater core.

Low coolant level

Can cause no heat from the heater core.

PAG oil, YF-specific formulation

Compatible with R-1234yf refrigerant.

Refrigerant recovery

Removing refrigerant and storing it safely.

Refrigerant recycling

Cleaning refrigerant for reuse.

Refrigerant reclamation

Returning refrigerant to original purity standards.

Receiver-drier

Prevents liquid refrigerant from reaching the compressor in a TXV system.

Pressure relief valve

Vents refrigerant if pressures become excessive.

Black death

Caused by compressor failure producing debris.

Vacuum pump

Tool used to evacuate an A/C system.

A/C clutch

Engages and disengages the compressor.

190–220°F (88–104°C)

Typical engine operating temperature range.

Coolant overflow reservoir

Allows expansion and contraction of coolant.

Ethylene glycol vs propylene glycol

Difference in toxicity and environmental impact.

Engine overheats under load

Common symptom of a partially clogged radiator.

Weep hole

Indicates seal failure/leakage in a water pump.

Hydrometer

Test that checks coolant freezing/boiling protection.

Mixing different coolant types

Can cause sludge formation and corrosion.

Fan clutch

Engages cooling fan only when needed.

Low coolant or air pockets

Causes heater output to fluctuate while driving.

Overcharging refrigerant

Causes high pressure and poor cooling in A/C systems.

Correct O-rings

Important to prevent leaks in A/C systems.

Thermal expansion valve hunting

Constant opening and closing of the TXV.

Restricted radiator or coolant flow

Likely cause of overheating at highway speeds.