Originally Posted By: DoubleWasp
The trade is not trying to keep itself a secret. People keep it a secret from themselves, and companies that make "ez duz it" AC fixes throw even more kitty litter over the whole thing.
Most people look at the cost of purchasing the correct equipment and immediately decide to half-moon the process. Lacking the proper information and tools, they usually end up destroying the whole system.
Knowing this, companies make completely inadequate products to service AC systems, often leading to disaster. If your system needs a 26 oz. charge of refrigerant, you are in deep trouble that a simple recharge will not fix. Charging a system using only the low-side pressure, with absolutely no temperature/humidity reference is insane. Stop-leak refrigerant should be banned. Ever seen what an orifice tube looks like after that garbage goes through it?
Of all of the times I have told people that they needed a complete system service, more often than not, they want a half-measure performed.
This x 1000. A/C is no big secret, it's not a conspiracy or a special club and it's not actually hard to do *right*. Like anything, you need a bit of know-how and tools, and it's a bit harder than it used to be to half-arse either the knowledge or the tools. Modern systems are fussy, precise and clean. (Did I mention clean?)
To service A/C you can do it two ways.
A) Read the bloody instructions and use the right tools. When it says Vacuum the system to 700 microns, get a [censored] micron gauge and do it right. Your harbour freight pneumatic vacuum pump won't ever get within a bulls roar of that, so get a cheap dual stage rotary oil sealed pump. When it says add 500g +/-25g of refrigerant, DO THAT. Exactly!. Figure out how much your hose & gauge set holds, put the bottle on a set of vaguely accurate scales and weigh it in properly. If you follow the instructions and use the right tools you don't actually have to learn anything, think, or do much more than grunt and twist knobs. Most knuckle draggers can get that far and not cock it up.
B) Learn how refrigeration systems work. They're not rocket science and simply rely on some very well known laws of thermodynamics. If you do that, then you can start using gauges and actually assessing system performance because you'll know what the numbers mean. Hint. Low side gauges that say "good/low" are useless under *all* conditions. Unfortunately to do this you have to read a bit, ask some questions and be willing to fight through the knuckle draggers responses "ugh, I just use 5 ov em blow off cans and it's rool cold" to get actual scientific answers and learn a bit about how the tools work and why the tools work. There are *loads* of good books out there in paper and pdf and forums are full of people with actual knowledge. (They're also full of blowhards who know enough to parrot something the read somewhere else, but a bit of critical thought soon has you seeing through that).
You can't just squirt a bit of gas in there and expect to get it right (although you can get extremely lucky and not hydrolock a compressor and get a passably working system). How do you know how much leaked out? Why did it leak out? Where did it leak out? Did you fix the leak? If you put gas in it now, how much will be in it tomorrow?
If you don't want to follow the instructions or actually invest in some tools and knowledge, then get a "pro" to do it. Thanks to the wonders of E-bay, the tools are affordable (although a recovery machine is getting a bit spendy. Still, do you want to do it right?).