Last week, my car's aircond could not work even when I turned it on. There is the sound from the aircond but no air is blowing out. After around like an hour, i started the car again and the aircond worked.

The next day when I was driving the car, I revved the car until 5000rpm and exactly when it reaches 5000rpm, a loud rubber screeching sound is coming out from the engine. I tried doing it for 2 or 3 times and the same thing happens. Later when I stopped my car, I rev the engine again...