F 350 2WD Super Duty V8-6.4L DSL Turbo (2009)
High Pressure Safety Valve HVAC: Description and Operation
Dual-Function Pressure Switch
Air Conditioning
Dual-Function Pressure Switch - 6.4L Diesel
The dual-function pressure switch includes 2 separate sets of contacts that are opened at 2 different pressures.
The first set of contacts in the dual-function pressure switch is used to interrupt A/C compressor operation in the event of excessively high discharge
pressure in the high-pressure side of the refrigerant system. The PCM monitors the first set of contacts in the dual-function pressure switch. When the
contacts are open, the PCM will disengage the A/C compressor clutch.
The second set of contacts in the dual-function pressure switch is used by the PCM to engage the high speed cooling fan. When the A/C pressure rises
above a preset level, the second set of contacts will close and the high-speed cooling fan will be engaged.
The dual-function pressure switch is located on a Schrader-type valve fitting on the compressor-to-condenser discharge line. It is not necessary to
recover the refrigerant to remove the dual-function pressure switch.
