Service Port HVAC: Description and Operation

Service Gauge Port Valve Description
The refrigerant system has a high-pressure (discharge) and a low-pressure (suction) gauge port valve. These are Schrader-type valves. They provide access to both sides (high-pressure and low-pressure) of the system for service hoses and a manifold gauge set so system pressures can be read.

High Pressure Side Gauge Port Valve Adapters

Service Hose Adapter Tools:

Rotunda High Side Adapter Set D81L-19703-A or Motorcraft Tool YT-354 or 355 or equivalent (illustration), is required to connect a manifold gauge set or charging station to the high-pressure gauge port valve.

Low Pressure Side Tee-Type Service Adapter Tool






A Tee-Type Service Adapter Tool, D87P-19703-A, is available for use in the low-pressure side of the refrigerant system when performing diagnosis to pinpoint the cause of a concern. The tool is shown installed in the illustration.
1. Disconnect the electrical connector at the clutch cycling pressure switch, and remove the switch from the switch fitting.

2. Install a new clutch cycling pressure switch and O-ring on the tee adapter tool and plan to leave it on the adapter as a permanent part of the tool. Be sure to lubricate the 0-ring before installation.
3. Install the tee adapter tool on the clutch cycling pressure switch fitting and tighten it securely.
4. Connect the low-pressure hose of the manifold gauge set to the side fitting on the tee adapter tool.
5. Connect the electrical connector to the clutch cycling pressure switch on the tee adapter tool.

With the tool installed in this manner, the refrigerant system can be operated under normal conditions with clutch cycling pressure switch control and evaporator (suction) pressure can be observed. This will give a more accurate low-pressure reading than can be obtained from a low-pressure gauge port located in the suction line or near the compressor.

After the repair has been completed, disconnect the manifold gauge set from the tee adapter tool. Disconnect the electrical connector from the clutch cycling pressure switch on the tool and remove the tool from the pressure switch fitting. Install the clutch cycling pressure switch and connect the electrical connector.

NOTE: Always replace the protector caps on the gauge port valves after servicing the refrigerant system.

Service Gauge Port Valve










A service gauge port valve assembly is shown in the first illustration with the valve in the closed position. The second illustration shows a gauge port valve in the open position with a manifold gauge set hose attached.