Ultimately, the only real way to know for certain is to evacuate the system, recover the refrigerant, and weigh what's recovered. Extremely high pressure on both sides of the system is a good indicator of it, as well. If you don't have the means to recover refrigerant or a manifold gauge set and the know-how to use it, cavitation (shaking) of the AC system when it's running is another telltale sign.
Yes!!! Most definately.
Yes, and an overcharged AC can cause devastating damage to the AC system. This is why you should have a certified shop perform this operation.
It might be overcharged. Or you might have contaminants in the system like air or acid.
Hydrofluorocarbon, chemicals used as refrigerants in automotive AC systems.
It shakes because it is overcharged. Needs some pressure released.
Usually a blockage in the system. Could also be overcharged, or have air in the system.
R-12 is the coldest
If an AC light is blinking on a 1991 Toyota Camry it may indicate that a belt is slipping. The AC light may also blink indicating that the system has been overcharged.
Take it to a garage that works on automotive ac.
AC compressors for one.
Bleed off some freon until you have the right numbers. This should be done by a qualified ac mechanic with equipment to reclaim the freon.
That depends on what kind of AC system it is (e.g., home, commercial, automotive) and when it was manufactured.