When my car’s compresser is on it is blowing cold air. When it cycles off and I am in idle it blows warm air, then the compressor comes back on it blows cold again...the mechanic said everything is working fine and there is the right frion weight. Not sure? Help please!

well, no car was designed that way. it has some kind of problems, like weak fan motors on the radiator or weak compressor or sensor failure, or just low on refrigerant . Have a REAL mechanic check it out if you want cold air at idle