Car a/c low pressure & high pressure service ports.
The car A/C system access ports are used to recovery/recharge, monitor and repair the air conditioning system. There are different automotive air conditioning service valve ports: The high side service valve port, low side service valve port, manufacturer assembly plant access port and ports for a/c pressure switches or sensors. The quality and safety standards for automotive air conditioning service valve ports are set by SAE J-639 and one of the principal goals is the ports to be designed in a way that refrigerant cross contamination would be almost impossible to happen.
The high side service port is a fitting that provides access to the high pressure side of the AC system and the low side service port is a fitting that provides access to the low pressure side of the AC system.
According to SCHRADER® , valves usually utilized for the high side service port are the Primary Seal Integrated Valve (two-piece valve) and the 10 mm Valve core (one-piece valve) and the low side valves usually utilized is the low side version of the Primary Seal Integrated Valve (two-piece valve) or the 8 mm Valve core (one-piece valve).
Types of service valve core.
The three positions valve is an old design no longer used in modern car ac systems. The three positions are: the front-seated position, the middle position,and the back-seated positions. The valve’s stem must be moved using a wrench. According to the position, the valve will give access to part or to the whole air conditioning system for recovery, service or repairs.
A/C Schrader® valves supplies two types of AC valve cores: valve cores within a separate port and integrated valve port. Valve cores consist of machined brass bodies with rubber seals that are screwed into a separate valve port. The core seal is attached to a pin which is actuated when contacted by the coupler depressor. The core is screwed into a port which is generally fabricated of aluminum that is brazed or welded onto the lines.
Service valve core sizes
The 10 mm core:this high flow core is used only in high side charge port applications where the high flow capability of this core can be of great value.
The 8 mm core:this medium flow core can be used on either the high side or low side charge port
The JRA core:this low flow core may be used on either the high side or low side charge port.
The Standard core:this core has been used extensively in switch & sensors port applications since the introduction of AC systems in mobile applications.
Schrader® recommends HNBR (Hydrogenated Nitrile Butadiene Rubber) material as the one that provides the greatest robustness in almost all applications. It is recommended among all other materials, like Neoprene or EPDM (ethylene propylene diene monomer rubber) because of its resistance to temperature, combined with compatibility with all mobile refrigerants oils, PAG and POE and mineral oil,.
What cause a valve core to fail?
Contamination is the greatest enemy of AC system durability, and of AC valve robustness. Temperature it is another factor that could easily damage any valve core. Temperatures above operating temperature aren’t recommended. Contamination could range from dirt, metallic debris generated during the installation valve core in its port, to air or moisture. Any debris inside the system will be pulled during the refrigerant recovery process and may become lodged in the valve causing it to remain open and leak. Very Often damage to a valve core happens after the a/c system has been serviced and the recovery/recycling /recharging machine has been disconnected from the service ports.
A/C valve core installation. How to prevent or minimize service valve core damage?
The successfully installation of an air conditioning valve core depends on great measure to valve core torque, lubrication and cleanliness. Extreme attention should be paid to cross-threading. Valve core should be tighten by hand the first turns and with the proper tools. A valve cap is important, because if is not fitted, dirt and water can enter the inside of the valve stem potentially jamming it or contaminating the sealing surfaces and causing a leak. These caps should be finger tight. There is no single cap torque recommendation. All ports include thread features to attach a closure cap. Security of this cap is essential to the leak integrity of the port. Accordingly these caps include a rubber seal around the port mouth. SAE J-639 requires that caps for HFO-1234yf charge ports be tethered to prevent loss, this is because of 1234yf mildly flammability.