how old is the car? Start the car and look at the window indicator on top of the drier, If its clear then there is not enough refrigerant in the sytem. if it has leaked out you will have to get it vacuumed and then recharged. In order to recharge it you will need the guages and know how to read them, While recharging you must monitor the drier, the window on the top will be milky white when its sustaining. You might just have some bad O rings, so check out the hoses for any signs of moisture.