SO for a while now, my wife's 2014 Passion hasn't been able to use the AC. when the car has been running for a bit, and comes to a stop light, a loud thunk thunk thunk goes on under the hood. If we attempt to turn the AC on, the same noise happens. I took the hood off today, and got the same result when running the AC. I did note the coolant reservoir was shaking erratically as well, but was definitely not the source of the noise. Does anyone know what this might be? I assume a busted connector or something. 44k miles on it, only had it for 3 years.