Air Conditioning – Keep Your Cool

For about eight years I drove a pickup truck with no air conditioning. Actually, it had air conditioning, but it didn’t work. I figured I could take it to a mechanic and have them repair it, but the truck wasn’t worth that much.  So, I had what is known as “240” air conditioning. That is, two windows rolled down at 40 miles per hour.  I went without “air” most of the time. It wasn’t too bad,  but nowadays it is rare to find a car or truck that does not come with air conditioning. This article will explain how air conditioning works and what to do if your air conditioning is broken.

How Air Conditioning Works

I used to think that air conditioners somehow made cold air and then blew it out into the cabin of the car. Not so! When I became a mechanic, I learned the errors in my thinking. Actually, the job of the air conditioner is to remove the heat from the air in the cabin of the vehicle. What follows is a really simplified explanation of how air conditioning works.

The air in the cabin is circulated, using fans, and the goal is to push the air over a radiator-like device called the evaporator. Inside the evaporator (and all of the air conditioning lines) is a gas called refrigerant. As the gas enters the evaporator, it expands and evaporates. The evaporation process requires heat, which it pulls from the air around the evaporator. So the cooler air is then blown through the cabin and is replaced by warmer, recirculated air.

The refrigerant is now under low pressure and travels to the compressor (powered by the engine under the hood). The compressor compresses the gas and sends it back to the evaporator to start the process all over. As the air circulates in the cabin, it slowly loses its heat.

Roll Up Your Windows and Recirculate the Air

Because the air conditioner is mainly trying to remove the heat from the mass of air in your vehicle, it is best to try to trap the air as much as possible. If the windows are open, the air conditioner will try to cool the entire world outside of the car as well. You want to keep the mass of air inside the cabin. That way, it will cool down faster.

Also, be sure to click the recirculate button. Most air temperature control centers on the dashboard of a vehicle will have some sort of re-circulation button.  This will pull the air from inside the cabin and recirculate it. Otherwise, the air conditioning system may pull warm air from outside of the vehicle into the cabin. That defeats the purpose.

When the Air Conditioner Goes Bad

The most common reason why an air conditioner no longer makes the air cooler is that refrigerant leaks out of the system. Without that special gas, evaporation will not fully occur (at the amount it is supposed to), and the air will not lose as much heat.

This can usually be fixed by adding refrigerant to the system. You can buy a can of refrigerant at automotive or general stores and try to replace it yourself. This sometimes works and is a low-cost alternative to having a mechanic do it. I tried this, but it did not work for me.

Refrigerant can escape around the bearings in the compressor or a hole somewhere in the line.  These are the most common causes, and you will generally need to take the car to a mechanic to get this fixed. Mechanics will have to “pull a vacuum” on the system, meaning they have to make the repairs and then suck out all of the air with a vacuum pump. Not many people have this in their garage.

Keep Your Cool

So remember, close your windows and click the recirculate button when using air conditioning for best results. And, if it is not as cool as it used to be, you can try replacing some of the refrigerant, or you may need to take it to a mechanic. Happy motoring and stay cool!


Written by Gary Pradel