Your a/c system is self contained and does not need maintenance. If the air comes out cold, you are done, and you don’t have to worry about this system. If the air comes our cool, or warm there are two possible problems with the system.
Why Doesn’t My A/C Work?
First possibility: The system may not have enough a/c refrigerant to enable a/c compressor to engage. Under the best of circumstances an a/c system slowly loose its refrigerant. It takes somewhere around 7 years for a perfectly good a/c system to leak enough refrigerant such that the compressor will not start when you try to get cold air. The oil which lubricates the a/c compressor floats in the refrigerant. As the refrigerant leaks out, the oil leaks out. If the compressor engaged when there was inadequate amount of refrigerant, the compressor would not be properly lubricated, and it would seize-up. To prevent this from happening, a pressure sensor prevents the a/c compressor from running when you are low on refrigerant.
On a side note, to keep the compressor lubricated in the winter, the computer turns the compressor on and off.
Also, when you turn on the “defrost,” the a/c system automatically turns on. The air first goes through the a/c coils in order to “dry-out” the air, and then the air is heated by the heating coils so that it can evaporate the condensation on the windshield.
Second possibility: The system is full of refrigerant, but due to an electrical problem, the a/c compressor does not turn on. For example, you could have a bad button (on the dash), bad relay, bad fuse, bad wire, or a bad sensor.
How Do I Diagnose a “Non-Operating A/C System?
I start by connecting my A/C gauges to your car. If the lower pressure gauge indicates good pressure (oddly enough good pressure in ‘psi’ is equal to room temperature) then the car is full of refrigerant. If I read good pressure but the a/c compressor does not engage, I know you have an electrical problem.
If the gauges indicate you don’t have any refrigerant, or a very low quantity of refrigerant then I add refrigerant and yellow dyed oil. If the compressor engages, then I know the electrical system is good, and the system did not work because of “Low refrigerant.” After I fill the system, I look for a refrigerant leak. Looking through tinted yellow glasses I can see refrigerant leaking from your system. Unfortunately, this only allows me to see “Big” leaks.
A small leak takes 3 days to two weeks for the system to loose enough refrigerant such that the a/c compressor no longer engages. Within days of the A/C no longer working, you need to bring your car back here so I can use my geeky yellow glasses to find the oil leaked. The oil leaked at the same spot where the refrigerant leaked. Once I see which part leaked, I can give you a price to replace that part.
Why Do I Have to Refill MY A/C System Once a Year?
You may have a seal around the a/c compressor which shrinks when the temperature gets cold (winter) and allows the refrigerant to leak out. When it is warm outside (summer) the seal expands and no longer allows the refrigerant to leak. You fix this by replacing the a/c compressor, or you refill the system every summer.
Why Shouldn’t I Refill the A/C System in the Winter?
If you wait weeks before bringing your car back, the yellow dye with disappear and I will not know form where the refrigerant leaked. It is for this reason that I hesitate refilling the a/c system in the late fall, winter, or early spring. If it refill the system, and you don’t use it for a month, the refrigerant may have leaked out and you didn’t know it since you did not use it. Months go by before you realize the a/c leaked, and by then I cannot see any trace of the yellow oil.