97' Pajero 2.5TDi. Aircon prob.nEEd Help pls

Car aircon only works when moving

No cold when idling even if it is in frost Mode in the control panel.

What is the prob?

what must i do?

Tnx.Bro's

check to see if the a/c fan come on mine does the same and its because there is no air going in through the condenser try reving the engine up while stopped and see if it gets colder sorry if this is late im new and was just looking through past threads