Car A/C Repair and Maintenance

In the Northern Hemisphere, Summer is upon us, and it is time to talk about the car a/c repair and maintenance. If you have visited my blog in the past, you know I love to guide people toward preventative maintenance instead of expensive repairs.

This philosophy applies to your car a/c. How many people alive now can go without a functioning vehicle a/c when the temperature hits 90 degrees Fahrenheit. It is unbearable.

Living poor in the Southern United States, we never had a functioning a/c in the car or the house.  It was early adult-hood before I had a window unit a/c in my apartment that cooled one room. I was almost thirty before I owned a car with a functioning a/c. I find it hard to get into a vehicle after the vehicle has been sitting in the sun all day with the interior temperatures soaring past 140 degrees Fahrenheit.

A little about the A/C system in the car

It doesn’t matter which a/c refrigerant your car system uses; the same essential components will make up your automotive a/c system.

R-12 refrigerant is almost non-existent today. If you have a can, sell it online and turn a profit while you still can. It is worth its weight in gold.

Most car systems still use R-134A. This refrigerant is being discontinued. It takes about 13 years to break down in the atmosphere.  Everything these days is geared toward being environmentally friendly so the powers that be have created a replacement that starts breaking down around 11 days.

R1234yf is now the industry standard. What does this mean for you? It means paying a little more for refrigerant when you need to replace it. You shouldn’t tell the difference in the performance of your a/c system. Component number one in the a/c system is one of these refrigerants.

The refrigerant circulates through a sealed system. In this system, you have a high-pressure side and a low-pressure side. The compressor pumps pressure into the system, and the orifice tube/expansion valve creates a pinch point. This pinch point slowly releases the pressure, creating a high-side and low-side.

The following diagram explains the parts of the auto a/c system. Courtesy of

a/c repair and maintenance
Typical auto a/c system

The parts: quick definitions


This piece provides the pressure. It is belt-driven. On a hybrid or newer car, it may be an electrically powered pump. The high- and low-sides connect to it. The internal piston pumps the refrigerant into the high-side as a gas. The coolant returns through the low-side as a gas.


This piece sits at the front of the vehicle. The engine fan pulls air through the condenser which removes the heat from the refrigerant and transforms it into a liquid.

The receiver dryer/accumulator

 This item filters the refrigerant and removes any moisture that may build up in the system. The refrigerant remains a liquid at this stage.

Expansion valve/orifice tube

This component restricts the flow and creates the high-side and low-side. The refrigerant remains a liquid.

The evaporator

This component, with the help of a blower, removes the heat from the passenger compartment. The refrigerant heats up and returns to the gaseous state.

Other important parts

A high-side port/tap and a low-side port/tap gives you access to service the refrigerant. You can find the ports on the lines.

The lines connect all the components of the system. The low-side lines are larger than the high-side lines.

The evaporator temperature sensor is located on the evaporator. It helps monitor the system temperature. It will cycle the compressor on and off to maintain the temperature above freezing.

The pressure sensor is located on the high-side. It will shut down the compressor if the pressure gets too high. This sensor also cycles the engine fan from low speed to high speed to regulate the pressure.

Problems that can occur


The system needs to remain sealed. Any of the system components can develop leaks. Sometimes a two-dollar seal can fix a problem.  To locate a system leak, you can use an electronic leak detector, or inject dye into the system and use glasses and a UV light to find the leak. If one of the main components are leaking, you will need to replace the leaking part.  This can be expensive.

Component failure and repair

 The compressor can fail. It has internal moving parts which can lead to wear and tear. The piston can bend or break, the front bearing can wear out, or it can leak. If the compressor uses an old-style clutch pulley, you can usually replace this part if it fails. Anything else, and you will need to replace the entire compressor.

The condenser can be damaged if your car is involved in a front-end collision, or it can be hit by a piece of flying debris. If this occurs, you will need to replace it.

The expansion valve/orifice tube can clog or fail.  It will need to be replaced.

The most common problem with the evaporator is leakage. Being in the dash of the car makes this repair labor-intensive.


Moisture can develop within an a/c system. It is a great idea to service your a/c system every two- to three- years. A service involves hooking up an auto a/c machine to the service ports and removing the refrigerant from the system. Next, the machine pulls a vacuum on the network to boil any moisture out of the system. The device will filter and clean the refrigerant. Then, the machine recharges the system with refrigerant and oil.  Most automotive shops will use a dye-based PAG oil to expedite finding future leaks. By performing this maintenance every few years, you reduce your chances of component failure.

I am sorry for being a little late with this week’s post, but we had a family friend die unexpectedly. I hope this information helps. Please leave me some comments and let me know how I am doing.

Until next time,

That Awesome Auto Guy

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