I hear this when i am at idle. The sounds is comming form outside the car. When i turn my air conditioning or heater on my car makes a clicking noise. it speeds up with the rev. it sounds like somehting is hitting a moving part, but i dunno what it could be. Any input would be helpful. Thank you.

your a/c compressor sounds low on freon. Nissan compressors will click when they little to no freon in them. Check levels and for leak. My old maxima se would click even with the heat when it was low on freon.