mmarshall

Now that the weather is getting cooler, some of you may not be running the air conditioning in your cars much anymore. It is important to turn the compressor on and run it for at least 5-10 minutes a week. That will keep the the moving parts lubricated and the seals from deteriorating and causing freon leaks.

With most cars nowadays, the compressor comes on automatically with either the air-conditioning or front window defrost mode. If it is cool outside, most systems nowadays let you add heat from the temperature control to keep from having an Arctic blast on you while it's running. And even more important...when the defrost is on and blowing air on the windshield, make sure the fresh-air intake is set to outside air (never use recirculate-mode with defrosting), as that will fog up the windows for sure), and add a little heat to keep the compressor from blowing cold air onto the windows and causing condensation on the outside. Again, with many new cars, the fresh-air mode automatically comes on with the defrost.....you don't have to switch it over manually. And, with automatic-climate-control systems, much of the rest, of course is just that....automatic, but you still have to turn the system on and off manually and select what mode you want.

Anyhow, the main idea, no matter how the system operates, is to make sure the compressor runs at least 5-10 minutes a week during the cooler months, to keep from deterioration and leaks. And you do want to keep leaks from happening, especially those of you with pre-1994 cars that have not been converted to newer R-134 freon. Older cars have the R-12 freon, which is hard to get now, and expensive to replace if it leaks out.

PhantomZX

I don't know if it applies to cars too, but I've heard that with home AC systems, the lubricating oil is too thick to flow properly when it's cold and could end up damaging the system.

To be on the safe side, make sure the engine warms up before running the AC if it's cold outside.

Threxx

My 335i's auto climate control almost NEVER turns off the A/C compressor in the winter... at least looking at the light... I don't know if it actually stays engaged the entire time or not. On longer trips I typically turn it off manually to increase mileage 1.5-2mpg unless the interior is fogged up.

mmarshall

If that were the case, then auto engineers would not hook up the compressor to the windshield defrost. You have to use the defrost to help clear the windshield on cold mornings with ice. Some cars, however, like my Outback (one of many reasons I like Outbacks) have electrically heated wires in the windshield down around the wipers, controlled by a separate switch, to get a head start on the hot-air defrost.

The reason the engineers hook up the compressor to the defrost is to provide a source of dry air to evaporate ther moisture. Unfortunately, this has a down side.....you have to ad heat to the defrost to keep the compressor from over-chilling the window and causing condensation on the outside of the glass. Using the recirculate-mode with defrost used to be a problem too....until the engineers also hooked up the defrost mode automatically with the fresh-air intake.


But, with ice on the windows, you have to be able to see first. That means using the defrost...which, on most newer cars, means the compressor to....cold or warm.


If the windows are clear and you don't have to let it idle while you use the defrost first, the engine warms up most efficiently when you give it thirty seconds to a minute to warm, shift into gear, and drive off slowly. That helps warm up the transmission too, not just the engine.

mmarshall

In that case, you don't have a problem, and this thread probably doesn't apply to your situation. That's why I aimed it mostly at manual-unit cars.

bruce van

Thanks for the tip mmarshall. Good to know.

darkdream

Oh i didn't know this.. I thought it was bad that I never shut off my A/C in the car haha...

Nextourer

Having the light on in automatic climate control systems just means that the A/C will be controlled automatically. If it's off, then it'll remain off and the system will operate everything else automatically and leave the A/C off.

Thanks for the tip mmarshall!

bad co

i keep my ac on all year long a/c not only cools the car but removes humidity i hate humid air

newr

My AC is always on whether it's summer or winter.