Q: Engine vibrates when aircon is on and vibration increases specifically in traffic

when i turn the aircon on i felt some vibration that goes on and off. vibration increases increases specially in traffic with a pounding noise and the aircon becomes a blower. air flowing out of the aircon is no longer cool even if i swicht it to maximum cool. what do you think is the problem, pls help me. thanks

我的汽车有21715英里。
我的汽车有自动变速箱。