A broken air conditioning schrader valve in your passenger compartment cooling system will either not permit refrigerant to be added to the system, not allow a pressure reading to be taken or leak out the refrigerant in the system. The air conditioning schrader valve can become damaged if the cap that is supposed to be on it is missing and dirt or debris becomes lodged inside of it. This situation will prevent it from operation as designed by opening and closing when the pin in the middle top of it is depressed. The most common failure is for the pin to stay in the depressed position allowing for the refrigerant to escape.
The air conditioning schrader valve is the same type of valve that is used in a tire stem to keep the air inside of the tire. This is a small diameter valve with a pin on the top that is supposed to return to the closed position by the spring located there. The material this valve is assembled from is many precision made steel alloy components. When the pin is depressed in the top of the air conditioning schrader valve, the piston in the valve body of this device is opened which permits the flow of refrigerant to occur.
To replace a faulty air conditioning schrader valve requires a special stem removal tool. If the technician is careful they can utilize a pair of needle nose pliers if the ends of the pliers are small enough or a pair of tweezers can be used in some instances. Once the air conditioning schrader valve is removed, all of the contents in the system will escape and have to be replenished for the a/c system to be functional again.