My ac will still cool my truck, but does not feel as cold as normal.
You have to remember, when you first get inside a standing car with the windows rolled up during a blistering sunny day, temps inside can reach as high as 140 degrees! Even setting solid ice inside that kind of heat, it will take a little while to melt. Conversely, firing up your AC into all of that heat, it will take a while to fully cool your vehicle's interior. (the larger the cabin area, the longer it will take to fully cool)
A few tips:
crack your windows if the car is sitting in direct sunlight for long periods...leaving the windows cracked can reduce the heat build up
use a dashboard sunscreen or a light reflecting window shade to cool the interior. That will keep the inside temps lower.
try running your A/C for the first few minutes with all the windows rolled down. Again, it reduces the amount of hot air inside and helps the car's A/C system cool off the interior quicker
don't run the a/c at its lowest point when the car is hottest. instead gradually lower the temp as the car cools...it makes the unit more efficient, and the air actually gets cooler faster.
finally keep your a/c system fully serviced. Each year get the system pressure tested, vacuumed, re charged if necessary, leak tested, expansion valves, orifice tubes, receiver/drier and accumulator routinely inspected/ replaced when needed. A good ac tune up service yearly should not run you more than 150.00 (not including Freon) and will keep your system operating at top efficiency.