Monday, April 29th, 2013

View from the Pumps: Car Air Conditioning System


Keeping your Car’s A/C Cold
by Gregg Marripodi

Greggs Automotive put together this post on how your car a/c system works because we understand the important role car air conditioning is to Punta Gorda residents in the summer months. If you have any questions please contact us.

Tis’ the season in Southwest Florida that people are most concerned with when they purchase a used vehicle. Does the air blow cold? A good salesman would smile and say politely “yes of course”, a salesman that we all were taught to avoid would answer, “yeah you can hang meat in there”. So typically if all you want is cold air, that’s doable. If you want cold air to last for more than a couple of months, takes a little bit more scrutiny. To have it work properly and not destroy expensive components during the course of “keeping the air cold”, takes a considerable amount of knowledge and an array of tools and equipment.

How the Air Cools

First, let’s talk about just how that air gets cold. The medium that does this, is of course Freon. You’ll notice that Freon is capitalized because it is trademarked by our friendly scientists from Dupont. Its real name is dichlorodifluoromethane gas. Dupont actually developed the R ratings based on the gas’ molecular structure which is why everyone thinks of R-12 when we speak of automotive Freon. Now we have R134a which is soon to be replaced by HFO1234yf.

Common Type of Freon

The most common type of Freon was R-12.Just how cold is Freon? R-12 boils at 28 degrees below 0. Ask yourself how many old time mechanics have frost bite in their fingertips because they mishandled Freon, better yet ask yourself how many died from phosgene gas poisoning, which is produced when you heat Freon with a butane or propane torch, because that is how we were taught to check for leaks. I told you that this is a tough business!

Laws of Heat Exchange

Cooling air is not a process of making something cold; it’s a process of removing the heat from the air that we want to cool us. This brings us right back to the natural laws of heat exchange. Air conditioning systems are the same as in your home and in your refrigerator. It consists of a closed system that recirculates a medium that is extremely cold and by the laws of physics attracts any heat from it’s surrounding area.

Okay back to air conditioning; here we are in our vehicles and we want some nice cool air so we can close the windows. So we pass some air over a heat exchanger, also known as an evaporator core, and we take the heat from the air so that now it’s “COOL”. So we’re all happy as clams in the vehicle because it’s cool. But now that nice cold Freon has become heated up from all the heat it just attracted from the incoming air. How do we make it cold again?

How Your Air Stays Cold

Here is the cycle; the heated Freon is sucked back to the compressor where it is compressed. It is then sent to the condenser as a high pressure gas where it condenses into a high pressure liquid. High pressure means high heat with Freon. It then passes through a restriction, also known as an expansion valve or an orifice tube that forces the pressure down, and makes the Freon cold again, and the cycle continues.

When I was just a young buck in New Jersey, I went to all the air conditioning classes and I thought to myself this is pretty simple. Because “the season” in New Jersey was only 2-3 months long it was a practice to just top off those systems that were not working properly and send them on their way. The following year we would see the same folks and do it all over again.

A/C is Crucial in Florida

When I moved to Florida in 1985 I really learned just how crucial it was for an a/c system to be properly maintained. But in the 70’s, the year of the gas shortage and the new mantra of everyone in America became “miles per gallon”. Like everything else in those vehicles, the air conditioning system was all downsized and made of aluminum, and THEN we found out about “GLOBAL WARMING “and how all that R-12 that was leaking from our cars was going to kill us and give us permanent sun burns. This led to the development of our latest Freon R134a.

Technicians had found that they had to take special classes, and buy expensive equipment to keep up with this new technology..

Next week we’ll bring you the REST OF THE STORY”

Gregg’s Automotive Maintenance & Repair Center

236 S. Tamiami Tr.
Punta Gorda, Fl. 33950
Auto Repair, A/C Repair, Oil Change, Brake Repair & Transmission Services