Parts of a Car AC System – Labeled Diagram with Names

All 13 parts on the diagram

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The whole system 9

Compressor It takes in low-pressure gas from the evaporator and squeezes it. That raises its pressure and its temperature. It then sends the gas to the condenser.
Condenser Outside air passing over it takes heat out of the hot gas. The gas turns back into a liquid.
Receiver-drier It collects the liquid and takes moisture and dirt out of it. It is also called the receiver-dehydrator.
Liquid line It carries high-pressure liquid, by way of the receiver-drier.
Expansion valve It lets a measured amount of liquid through and lowers its pressure. That also lowers its temperature.
Evaporator The cold liquid boils inside it. It soaks up heat from the air blown across it. That air is what cools the cabin.
Suction line It carries low-pressure gas.
Blower It pushes cabin air or outside air across the evaporator. The air goes out through the vents.
Vents The cooled, dried air comes out here.

Compressor and receiver-drier 4

Compressor clutch It is a magnetic clutch. Switched on, it locks the belt-driven pulley to the compressor's shaft. Switched off, it lets go and the compressor stops.
Drive belt It brings the drive from the engine's crankshaft.
Sight glass It lets a mechanic see the liquid going by. Not every system has one.
Desiccant It soaks up any moisture in the system.

How this list was compiled: Part names checked on 2026-09-30; a name is kept only when two independent sources use it. (1) US Army TM 9-8000, Principles of Automotive Vehicles, 1985, chapter 37, https://archive.org/details/tm-9-8000-principles-of-automotive-vehicles-1985 (compressor and its magnetic clutch, condenser, receiver drier or receiver-dehydrator with its filter, desiccant and sight glass, high-pressure lines and hoses, expansion valve, evaporator, low side and high side). The Navy's Construction Mechanic manual repeats this chapter's wording and is counted with it. (2) Wikipedia, Automotive air conditioning and Thermal expansion valve, text only (compressor driven by a drive belt through an electric clutch, condenser, receiver-drier with desiccant, expansion valve, evaporator, a fan blowing air across the evaporator, vents, liquid line, suction line). (3) Dade County Public Schools, Automotive Air Conditioning and Heating, course outline, 1973, ERIC ED092709, https://archive.org/details/ERIC_ED092709 (evaporator, compressor, condenser, receiver/drier, expansion valve, magnetic clutch, blower control, sight glass, suction line, liquid lines, belts and pulley). (4) Three car makers' owner's manuals, read as plain text copies held by this project (air conditioning compressor, condenser, drive belt, blower). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's system, nothing traced. Licence: own work

How it works

The parts of a car AC system form one closed loop. Refrigerant goes round it again and again, picking up heat inside the cabin and giving it up to the air at the front of the car.

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Follow the loop

Start at the compressor, which squeezes the refrigerant gas. The condenser at the front cools it into a liquid. The receiver-drier cleans and dries it, and the liquid line takes it to the expansion valve. In the evaporator it turns cold and soaks up heat from the air the blower pushes to the vents. The suction line returns it to the compressor.

Two close-ups

The second view shows the front of the compressor, with its clutch and the drive belt, and the receiver-drier cut open, with its sight glass and desiccant.

The dashed line stands for the wall between the engine bay and the cabin. The evaporator, blower and vents are on the cabin side.
Some cars have an accumulator and an orifice tube where this one has a receiver-drier and an expansion valve.

Questions and answers

What are the main parts of a car AC?

Five parts in a loop: compressor, condenser, receiver-drier, expansion valve and evaporator, joined by pipes and hoses. A blower pushes cabin air across the evaporator and out of the vents.

What does the compressor do in a car a/c system?

It is the pump. A belt from the engine turns it through a clutch. It draws in low-pressure gas from the evaporator and sends it on to the condenser at high pressure and high temperature.

What is the difference between the condenser and the evaporator?

They are both finned coils, doing opposite jobs. The condenser is at the front of the car and gives heat away to outside air. The evaporator is inside the cabin's air box and takes heat out of the cabin air.

Which parts of an AC system in a car are inside the cabin?

The evaporator, the blower and the vents, all in or on the air box behind the dashboard. The compressor, condenser and receiver-drier are under the hood.