How does my A/C only work when my CRV 2004 is moving?

If the compressor is kicking on and off, you may just be low on refrigerant.

Thanks but I don't think so. The mechanic said I need a new compressor but couldn't answer me as to why it works perfectly when I'm driving. What is it about a moving car that changes how the compressor works?

How cold the air is has nothing to do with the fan, just because the mechanic said it needs a new compressor doesn't mean it really does. Like KenF said before, it is probably low on refrigerant. I would take it to a different mechanic, one that specializes in A/C repairs. It will cool better at higher engine RPM when the refrigerant is on the low side. Next time you are at a stop light put the car in neutral and rev the engine and see if that helps it cool off.

Thanks. I had to do something so I changed the compressor and this involved draining and replacing the freon. God! Over a thousand bucks!