Refrigerant system service ports. Vacuum check valve

Refrigerant system service ports


The two refrigerant system service ports are used to charge, recover/recycle, evacuate, and test the air conditioning refrigerant system. Unique service port coupler sizes are used on the R-134a system, to ensure that the refrigerant system is not accidentally contaminated by the use of the wrong refrigerant (R-12), or refrigerant system service equipment.


The high pressure service port is located on the liquid line between the condenser and the evaporator, near the front of the engine compartment. The low pressure service port is located on the compressor manifold, directly over the suction port of the compressor.

Each of the service ports has a threaded plastic protective cap installed over it from the factory. After servicing the refrigerant system, always reinstall both of the service port caps.

Vacuum check valve


Two vacuum check valves are installed in the accessory vacuum supply line in the engine compartment.

One check valve is located near the vacuum fitting on the power brake booster. The second check valve is located at the heater and air conditioner take-out of the accessory vacuum supply line. The vacuum check valves are designed to allow vacuum to flow in only one direction through the accessory vacuum supply circuits.


The use of the vacuum check valves help to maintain the system vacuum needed to retain the selected heater-A/C mode settings. The check valves will prevent the engine from bleeding down system vacuum through the intake manifold during extended heavy engine load (low engine vacuum) operation.

The vacuum check valves cannot be repaired and, if faulty or damaged, they must be individually replaced.

    Dodge Durango (DN) 1998-2003 Service Manual


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