A/C is weak
I am not an automotive air conditioning expert, but generically speaking the common cause of weak cooling is loss of the cooling gas, compressor becoming weak, or a defective control valve; in that order. Most of the time in air conditioning systems they make a slow leak and eventually loose the cooling gas (freon). Automobiles are ******* the air conditioning system because of the roughness they have to endure with bumps, jarring around, and severe conditions. A common type of problem is the condenser leaking. The condenser becomes very humid all the time due to it being cold. The humidity promotes corrosion in its piping. The air conditioning service person will put in the gas with an ultraviolet dye, run the system for a while, and then examine the system using an ultra violet lamp. He will be able to see where the leaks are occurring and thus give an estimate for the parts that must be replaced. If you have an older vehicle, the air conditioning system can end up being rather expensive to service. With some of the common type faults don't be surprised if repairs can go in to a number of thousands of dollars, unless you are luck and the fault is a simple seal or gasket. Jerry G.