when 2001 ford explorer is idle ac doesn't blow cold air

2 things come to mind, low refrigerant and/or a worn compressor. Best thing to do is to put on a set of A/C gauges ( or have a shop so this ) and see what the idle pressures and then the 2500 rpm pressure are. This will tell you volumes about what your issue is. here is an A/C diagnostic sheet to help you or your shop: https://repairpal.com/estimator/air-conditioning-diagnosis-cost