I was recharging the A/C in an 04 Ford Mustang. When I went to recharge, I noticed the valve was leaking. So I went to Autozone and they gave me a replacement kit. However, the tool in the kit would not turn the core valve to remove it. I went back and they said there is only one size valve for all models. My question is am I doing something wrong? What is the proper way to replace this? It seemed easy.