Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Dual-Function Pressure Switch (4.6L and 5.4L)
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 in series with the A/C cycling switch. When the ACCS circuit is 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.
For specifications regarding operating pressure(s), refer to CLIMATE CONTROL SYSTEM - GENERAL INFORMATION AND DIAGNOSTICS .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.