1998 Dodge Caravan ac blows cold sometime and sometimes doe

1998 Dodge caravan 210541miles. Has dual ac, rear defogger, wipper. When ac works it blows really cold. It started messing up last year on me and it done it only a few times. Now it seems to be geting worse. But it seems when it gets hot after using, it stops blowing cold like the clutch is not ingageing. It started out just happening when i stop someplace turn off motor and when i came back it would not cool any more. It would have to sit over night and then it would be working fine again. Just a few weeks ago it stoped blowing cold while I was driving it and had to sit over night to start blowing cold again. We have check fuses, relays, all my lights work on the dash. We look over the control modular and nothing looks burnt on it or to connector.
Hope you can help!!!1