the ac in my 03 1500 ram works while im driving but when i come to stop it quits blowing cold. what could be problem?

Worn out compressor. Typically, they last around 100,000 miles.

A bad compressor will normally show the inability to generate enough suction and pressure at idle speeds. If the engine speed needs to be increased substantially to bring pressures in range, it's a sign the compressor is weak. The typical complaint is, "It only cools when the engine is revved or when driving down the road." It's often simple. If we hook, for example, the gauges up and see 80 psi on the low and high sides and the compressor hub is spinning, the compressor is shot. It's not producing suction or pressure. We could add more refrigerant and nothing would change. Compressors must be able to pull a vacuum and create pressure.

Attach a manifold gauge set and compare readings to spec.