Where do you connect to charge ac system on 2001 Chevy silverado truck?

The location of the AC system charging port on a 2001 Chevy Silverado varies slightly depending on the specific model and trim level, but it's generally located on the low-pressure side of the AC system, often near the compressor or condenser. It will be a schrader valve, similar to those on your tires, but typically smaller. It might have a cap on it.

However, I strongly advise against attempting to charge your AC system yourself unless you have experience working with automotive air conditioning systems and the proper tools. Refrigerant is under high pressure and improper handling can lead to serious injury or damage to the system. Improperly charging the system can also damage the compressor.

Instead of trying to do it yourself, I recommend taking your truck to a qualified mechanic or auto AC specialist. They have the necessary tools, knowledge, and safety equipment to properly diagnose and charge your AC system. They can also identify any underlying problems that may be causing the AC to malfunction.