AC Low Pressure Switch

This procedure removes and replaces the AC low pressure switch on the 2005 Dodge Viper 8.3L V10, which monitors refrigerant pressure and protects the compressor from damage.

Warnings

Tools required

Parts

• AC low pressure switch × 1 — Mopar 5033320AA or equivalent
• AC system O-rings (if switch uses O-ring seal) × 1 — Use OEM specification for refrigerant applications
• PAG oil for AC system × 1 — Use OEM-specified viscosity

Fluids

• R-134a refrigerant

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely if recently operated
3. Connect AC recovery machine to service ports and recover all R-134a refrigerant according to EPA regulations and equipment manufacturer instructions
4. Verify system pressure reads 0 psi on gauge set after recovery is complete

Procedure

1. 1

   Locate AC Low Pressure Switch
   Open hood and locate the AC low pressure switch on the suction line (larger diameter AC line) between the evaporator outlet and compressor inlet. On the 2005 Viper, the low pressure switch location should be confirmed against factory service documentation; it may be mounted on the suction/low-side line or on the receiver-drier assembly. Verify exact location and side before proceeding. The switch has a single electrical connector and threads directly into the AC line.
2. 2

   Disconnect Electrical Connector
   Press the locking tab on the electrical connector and pull straight away from the switch body. If corrosion is present, use a small flathead screwdriver or pick to gently release the locking tab. Do not pull on the wires themselves.
3. 3

   Remove Low Pressure Switch
   Using an appropriately sized wrench that matches the switch hex flats, unthread the low pressure switch counterclockwise from the AC line fitting. Be prepared for a small amount of residual refrigerant oil to drip from the port. Keep shop towels ready to catch any fluid. Once removed, immediately cap or cover the open port in the AC line to prevent moisture and debris contamination.
4. 4

   Inspect and Prepare New Switch
   Inspect the sealing surface on the AC line port for damage, debris, or old O-ring material. Clean the threads and sealing surface with a lint-free shop towel. If the new switch uses an O-ring seal (check both old and new parts), verify the new O-ring is properly seated in the switch threads. Apply a light coating of clean PAG oil to the O-ring or sealing washer to aid installation and ensure proper seal.
5. 5

   Install New Low Pressure Switch
   Thread the new low pressure switch clockwise into the AC line port by hand until finger-tight, ensuring threads engage properly and switch is not cross-threaded. Using an appropriately sized wrench, tighten the switch to the factory-specified torque (verify in service documentation; typically low, around 7-10 Nm / 5-7 lb-ft for O-ring sealed switches). Do not overtighten, as this can damage the sealing threads or crack the switch body. Note: AC Pressure Switch (verify factory torque spec)
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
6. 6

   Reconnect Electrical Connector
   Push the electrical connector firmly onto the new switch until the locking tab clicks into place. Gently tug on the connector to verify it is fully seated and locked.
7. 7

   Evacuate AC System
   Connect vacuum pump to AC service ports and evacuate the system to remove all air and moisture. Evacuate for a minimum of 30-45 minutes to achieve proper vacuum (29+ inches Hg). Hold vacuum for 10 minutes after pump shutdown to verify system integrity—vacuum should not drop, indicating no leaks at the switch or elsewhere.
8. 8

   Recharge AC System
   Using AC service equipment, recharge the system with the specified amount of R-134a refrigerant according to the underhood AC specification label. Monitor low pressure switch operation during charging—the compressor clutch should engage when system pressure reaches the switch's activation threshold (verify specific cut-in pressure in service documentation).

Reassembly

1. Verify electrical connector is fully locked onto new switch
2. Confirm no refrigerant leaks at switch installation point using electronic leak detector or soap solution
3. Check AC system operation in all modes to verify compressor cycles on and off properly

Verification

• Start engine and turn AC system to maximum cooling
• Verify compressor clutch engages and cold air blows from vents
• Monitor AC gauge pressures—low side should read 25-45 psi at idle with ambient temperature around 70-80°F
• Verify compressor cycles off if low pressure drops below switch threshold (system protection function)
• Check for refrigerant leaks at switch threads using leak detector
• Confirm no warning lights on instrument cluster related to AC system

Related trouble codes on this vehicle

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