AC Expansion Valve (TXV)

Replace the AC expansion valve (TXV) on a 2005 Dodge Viper 8.3L V10, requiring AC system discharge, evaporator line access, and refrigerant recharge.

Warnings

Tools required

Parts

• AC expansion valve (TXV) × 1 — Use OEM specification
• AC line O-rings × 2 — Use OEM specification
• PAG oil (appropriate viscosity for R-134a) × 1 — Use OEM specification

Fluids

• R-134a refrigerant

Preparation

1. Verify AC system has refrigerant before starting work (indicates system integrity).
2. Park vehicle on level surface and engage parking brake.
3. Ensure engine is cold before beginning work.
4. Gather all replacement parts and verify O-ring sizes match original fittings.
5. Connect AC recovery machine and verify it is functioning properly.

Procedure

1. 1

   Recover AC Refrigerant
   Connect AC recovery machine to both high and low side service ports. Follow machine instructions to fully recover all refrigerant from the system. Verify system pressure reads 0 PSI on both high and low sides after recovery is complete. Allow system to stabilize for 5 minutes and recheck pressure to ensure no residual charge remains. Record the amount of refrigerant recovered for recharge reference.
2. 2

   Access Passenger Side Footwell
   Remove the passenger side lower trim panel to access the evaporator housing. The expansion valve is located at the evaporator inlet on the HVAC housing; verify exact access location (engine-bay firewall side vs. passenger footwell) against the 2005 Viper factory service manual before disassembly. Check for fasteners securing the lower trim panel and remove them. Gently pull the panel away from retaining clips.
3. 3

   Locate Expansion Valve
   Identify the expansion valve at the evaporator inlet. The valve has two refrigerant lines connected: the high-pressure liquid line from the condenser and the low-pressure outlet to the evaporator. Note the orientation of the valve and sensing bulb position before removal. Take a photo for reference during installation.
4. 4

   Disconnect Liquid Line
   Using a flare nut wrench to prevent line damage, carefully loosen and remove the high-pressure liquid line fitting from the expansion valve inlet. Cap the open line immediately to prevent contamination. Inspect the O-ring on the line fitting and discard it (new O-ring will be installed).
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
5. 5

   Disconnect Evaporator Outlet Line
   Using a flare nut wrench, loosen and remove the evaporator outlet line fitting from the expansion valve. Cap the open evaporator port immediately. Inspect and discard the O-ring from this fitting as well. Keep the work area clean to prevent debris entry into the AC system.
   Torque spec

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

   Remove Expansion Valve
   Remove the mounting hardware securing the expansion valve to the evaporator housing or firewall bracket. Verify the exact number and type of expansion valve mounting fasteners against the 2005 Viper factory service manual before removal. Carefully withdraw the expansion valve, taking care not to damage the sensing bulb or capillary tube if it is an externally equalized valve. Inspect the old valve for signs of contamination or debris.
   Torque spec

   Expansion Valve10 Nm (7 lb-ft)
7. 7

   Inspect and Clean Mating Surfaces
   Inspect the evaporator inlet port and liquid line ports for debris, corrosion, or damage. Clean all mating surfaces with a lint-free cloth. Check that the internal screen (if present) at the expansion valve inlet location is not clogged with debris. If excessive contamination is found, the system may require flushing before proceeding.
8. 8

   Prepare New Expansion Valve
   Remove the new expansion valve from its packaging just before installation to minimize moisture exposure. Verify the valve is the correct type and capacity for this application. Check that the sensing bulb (if external) is properly secured and the capillary tube is not kinked or damaged.
9. 9

   Install New O-Rings with PAG Oil
   Install new O-rings on both refrigerant line fittings. Lightly coat each O-ring with fresh PAG oil of the exact viscosity specified for the 2005 Viper AC compressor (verify PAG grade against the OEM/compressor manufacturer specification before use). Do not over-lubricate; a thin film is sufficient. Ensure O-rings are seated properly in their grooves without twisting.
   ⚠Add approximately 1 ounce of PAG oil to the system during reassembly to replace oil lost during refrigerant recovery. Add oil to the new expansion valve or through the compressor fill port per manufacturer specification.
10. 10

    Install New Expansion Valve
    Position the new expansion valve in the correct orientation (reference your installation photo). Install and hand-tighten the mounting hardware. Torque the expansion valve mounting fasteners to specification. Ensure the sensing bulb (if external) is positioned correctly against the evaporator outlet line in the same location as the original.
    Torque spec

    Expansion Valve10 Nm (7 lb-ft)
11. 11

    Reconnect Refrigerant Lines
    Connect the high-pressure liquid line to the expansion valve inlet. Hand-tighten the fitting, then use a flare nut wrench and torque wrench to tighten to specification. Connect the evaporator outlet line to the expansion valve outlet and torque to specification. Ensure both fittings are properly seated and not cross-threaded.
    Torque spec

    AC Line Fittings20 Nm (15 lb-ft)
12. 12

    Evacuate AC System
    Connect the AC vacuum pump to the system service ports. Evacuate the system to a deep vacuum (minimum 29 inches Hg / 500 microns) for at least 30-45 minutes. Monitor the vacuum gauge; the vacuum should hold steady without rising, indicating no leaks. If vacuum rises, locate and repair leaks before proceeding.
13. 13

    Recharge AC System
    With the system under vacuum, close the valve to the vacuum pump and connect the refrigerant supply. Charge the system with the amount of R-134a recorded during recovery, or per the underhood specification label (confirm the exact R-134a charge for this vehicle from the underhood label or factory service manual before charging). Charge through the low-side port with the engine running and AC on maximum. Monitor system pressures throughout the charging process.
    ⚠Do not overcharge the system. Overcharging reduces cooling efficiency and can damage the compressor.
14. 14

    Leak Test System
    With the system fully charged, use an electronic leak detector to check all connections at the expansion valve and both refrigerant line fittings. Pay special attention to the areas just serviced. If a UV dye system is used, inspect with UV light. Any detected leaks must be repaired by discharging, correcting the issue, and repeating the evacuation and recharge process.
15. 15

    Reinstall Trim and Test Operation
    Reinstall the passenger side lower trim panel and secure all fasteners and clips. Start the engine and set the AC to maximum cold with the blower on high. Allow the system to run for 10 minutes. Verify cold air output at the vents (typically 38-45°F at the center vent with 70-80°F ambient temperature). Check that the compressor cycles properly and system pressures are within specification.

Reassembly

1. Trim panel installation is the reverse of removal. Ensure all clips are properly seated.
2. Verify no tools or parts were left in the passenger footwell area.
3. Confirm all refrigerant line fittings are torqued to specification and leak-free.

Verification

• Start engine and run AC on maximum cold for 10 minutes; verify center vent temperature is 38-45°F with ambient temperature 70-80°F.
• Confirm compressor clutch engages and disengages properly during operation.
• Check system pressures: low side should be approximately 25-35 PSI, high side 200-250 PSI at idle with 70-80°F ambient (varies with temperature and humidity).
• Listen for abnormal noises from the compressor or expansion valve (hissing at the valve is normal during operation).
• Verify no refrigerant leaks at the expansion valve or line connections using electronic leak detector.
• Ensure passenger footwell trim is secure and no rattles are present.

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