AC High Pressure Switch

Replace the AC high pressure switch on a 2008 Dodge Viper 8.4L V10, which monitors refrigerant pressure and protects the compressor from over-pressure conditions.

Warnings

Tools required

Parts

• AC high pressure switch × 1 — Mopar 68003946AA or equivalent
• O-ring for pressure switch (if not included with switch) × 1 — Use OEM specification

Fluids

• ac_refrigerant

Preparation

1. Park vehicle on level surface and apply parking brake.
2. Allow engine and AC system to cool completely if recently operated.
3. Open hood and secure in raised position.
4. Put on safety glasses and work gloves.

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to service ports (low and high side) following equipment manufacturer procedures. Recover all refrigerant from the system completely, pulling the system into a slight vacuum to ensure complete recovery. Verify system reads 0 psi or slightly below before proceeding. Document the amount of refrigerant recovered for recharge reference.
2. 2

   Locate AC high pressure switch
   The AC high pressure switch/transducer is located on the high pressure line (verify exact location against factory service information for this vehicle). The switch threads into the refrigerant line and has an electrical connector—verify the pin count before ordering parts. Identify the switch before proceeding to removal.
3. 3

   Disconnect electrical connector
   Press the locking tab on the electrical connector and pull straight away from the AC high pressure switch to disconnect. Set the connector aside where it will not be damaged.
4. 4

   Remove high pressure switch
   Using an appropriately-sized wrench (verify size on the switch flats) or an adjustable wrench, rotate the AC high pressure switch counterclockwise to unthread it from the refrigerant line. Be prepared for a small amount of residual oil to drain from the port. Remove the switch completely and inspect the O-ring seal.
5. 5

   Prepare new switch
   Inspect the new AC high pressure switch to confirm it has a fresh O-ring installed. If the O-ring is not pre-installed or appears damaged, install a new O-ring onto the switch threads. Lightly lubricate the O-ring with clean refrigerant oil to ease installation and ensure proper seal.
6. 6

   Install new high pressure switch
   Thread the new AC high pressure switch into the refrigerant line port by hand, turning clockwise. Once hand-tight, use the correctly-sized wrench to snug the switch to the factory torque specification (verify spec; typical O-ring pressure switches are approximately 5-9 ft-lbs). Tighten until the switch seats properly against the O-ring—do not over-tighten as this can damage the O-ring seal or strip the aluminum threads in the line.
7. 7

   Reconnect electrical connector
   Push the electrical connector onto the new AC high pressure switch until the locking tab clicks into place. Verify the connection is secure by gently pulling on the connector.
8. 8

   Evacuate AC system
   Connect vacuum pump to AC service ports. Evacuate the system to at least 29 inches of mercury (inHg) vacuum and hold for a minimum of 30 minutes. Monitor for vacuum decay—the system should hold vacuum without significant loss, indicating no leaks. If vacuum decays, inspect the new switch installation and all connections for leaks.
9. 9

   Recharge AC system
   With system still under vacuum, connect refrigerant supply (R-134a, correct for this model year) to service ports. Recharge to the factory-specified charge capacity for the 2008 Viper (verify capacity from underhood label or service info). Recharge the system with the amount of refrigerant documented during recovery, or per factory specification if topping up is needed. Use a refrigerant scale for accurate measurement. Do not overcharge the system.
10. 10

    Test AC operation
    Start the engine and turn AC system to maximum cooling with blower on high. Allow system to run for several minutes while monitoring pressures with manifold gauges. High side pressure typically reads roughly 150-250 psi at idle depending strongly on ambient temperature and humidity (consult a temperature/pressure chart). Verify compressor cycles properly and high pressure switch functions correctly. Check for cold air from vents.

Reassembly

1. No disassembly of other components was required for this procedure.

Verification

• Confirm AC system pressures are within normal range (low side 25-45 psi, high side 200-250 psi at idle, varies with ambient temperature).
• Verify AC compressor cycles on and off normally as controlled by the system.
• Check that cold air is being produced at the cabin vents.
• Inspect the new high pressure switch connection for any signs of refrigerant leakage using leak detector.
• Verify electrical connector is fully seated and locked onto switch.
• Confirm no refrigerant odor or visible oil around switch installation point.

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