AC Expansion Valve (TXV)

This procedure replaces the AC expansion valve (TXV) on a 2008 Dodge Viper with 8.4L V10 engine, requiring recovery of refrigerant, removal of evaporator components, and system recharge.

Warnings

Tools required

Parts

• AC expansion valve (TXV) × 1 — Mopar 55111545AA or equivalent
• Expansion valve O-rings × 1 — Use OEM specification
• PAG oil for AC system × 1 — PAG-46 per OEM spec
• AC system sealing caps × 1 — Use during service to prevent contamination

Fluids

• R-134a

Preparation

1. Park vehicle on level surface and set parking brake
2. Allow AC system to equalize to ambient temperature (at least 30 minutes after last operation)
3. Gather EPA-approved AC recovery equipment and verify proper function
4. Ensure work area is well-ventilated
5. Disconnect negative battery cable and wait 2 minutes for airbag system capacitor discharge

Procedure

1. 1

   Recover AC refrigerant
   Connect AC recovery machine to both high and low side service ports. Follow machine operating procedure to recover all refrigerant from the system. Document the amount recovered. Once recovery is complete and system shows vacuum or 0 PSI, close service valves and disconnect machine. Verify the factory R-134a charge amount from the underhood AC specification label or service manual for this specific vehicle.
2. 2

   Access passenger side footwell
   Determine the correct access point for the HVAC evaporator/TXV on this vehicle (footwell vs. firewall) and remove the appropriate trim or firewall components per the service manual. The panel is retained by fasteners along the top edge and may have push clips along the bottom edge. Carefully pull the panel away from the dash structure and set aside.
3. 3

   Locate expansion valve
   The expansion valve is mounted on the evaporator inlet, accessible from the passenger footwell area near the firewall. Identify the two refrigerant lines (liquid line from condenser and suction line to compressor) connected to the TXV body. Note the orientation of the valve and the routing of the thermal bulb if externally mounted. Take a photo for reference during installation.
4. 4

   Disconnect liquid line from TXV
   Using appropriate wrench size, carefully loosen the liquid line fitting at the expansion valve inlet. This is the smaller diameter line coming from the condenser. Once loosened, completely remove the fitting and immediately cap both the line and the valve port with clean sealing caps to prevent moisture ingress. Remove and discard the O-ring from the fitting.
5. 5

   Disconnect evaporator outlet from TXV
   Loosen and remove the fitting connecting the expansion valve outlet to the evaporator. This connection may use a block fitting or threaded connection depending on exact configuration. Cap the evaporator opening immediately. Inspect the connection area for signs of oil weeping or debris that would indicate previous contamination or leakage.
6. 6

   Remove thermal bulb (if external)
   If the expansion valve has an external thermal sensing bulb clamped to the suction line, carefully remove the clamp securing it. The bulb is fragile and connected to the valve body by a capillary tube. Handle with care to avoid kinking or damaging the capillary tube. Note the exact position on the suction line for reinstallation.
7. 7

   Remove expansion valve mounting
   Remove the fasteners securing the expansion valve bracket or body to the evaporator housing or mounting location. The valve may be held by 2 screws or bolts. Once fasteners are removed, carefully extract the valve assembly from the evaporator case, taking care not to damage the evaporator core fins or tubes. Remove any remaining O-rings from the evaporator connection points.
8. 8

   Prepare new expansion valve
   Unpack the new expansion valve and verify it matches the original in configuration and connection types. Lubricate all new O-rings with clean PAG-46 oil. Install new O-rings on the valve connections, ensuring they seat properly in their grooves. If the valve has an adjustable superheat setting, verify it matches the specification for this application (typically factory preset and non-adjustable on this platform).
9. 9

   Install new expansion valve
   Position the new expansion valve into the evaporator case mounting location, ensuring proper orientation with inlet and outlet ports aligned to their respective lines. Install and tighten the mounting fasteners to secure the valve bracket. Verify the valve body is stable and properly supported before connecting refrigerant lines.
10. 10

    Connect evaporator to TXV outlet
    Remove the cap from the evaporator connection and the new valve outlet. Install a new lubricated O-ring on the fitting if not already installed. Thread the connection by hand to ensure proper alignment, then tighten with a wrench. Use two wrenches (one to hold the valve body, one to tighten the fitting) to avoid twisting the valve or evaporator tubes.
11. 11

    Connect liquid line to TXV inlet
    Remove caps from the liquid line and valve inlet. Verify the new O-ring is properly seated and lubricated. Thread the fitting by hand, then tighten with appropriate wrenches while backing up the valve body to prevent stress on connections. Ensure connection is snug but do not overtighten and risk crushing the O-ring.
12. 12

    Install thermal bulb (if external)
    If applicable, position the thermal sensing bulb on the suction line at the same location noted during removal (typically on the horizontal run of the suction line after the evaporator, at the 4 o'clock or 8 o'clock position). Secure with the clamp, ensuring good thermal contact but not overtightened to avoid damaging the capillary tube or suction line.
13. 13

    Reinstall passenger trim panel
    Align the lower dash trim panel and press any push clips into their receivers. Install the Torx fasteners and tighten securely. Verify the panel is flush and all fasteners are secure. Reconnect the negative battery cable.
14. 14

    Evacuate AC system
    Connect vacuum pump or AC machine in vacuum mode to both service ports. Evacuate the system to a deep vacuum (minimum 29 inches Hg) and hold for at least 30 minutes. Monitor for vacuum decay which would indicate a leak. If vacuum holds steady, the system is ready for recharge. If vacuum decays, locate and repair leak before proceeding.
15. 15

    Recharge AC system
    Using refrigerant scale and AC machine, charge the system with the documented amount of R-134a recovered (or the factory specification listed on the underhood AC label / service manual if records are unavailable). Add the PAG oil quantity and viscosity specified by the service manual for this vehicle to replace any oil lost during service. Follow machine procedure for liquid or vapor charging as appropriate. Verify both high and low side pressures are within specification after charge is complete.

Reassembly

1. All reassembly steps are included in the main procedure
2. Verify all refrigerant line connections are tight and properly torqued
3. Ensure thermal bulb (if equipped) has proper contact with suction line

Verification

• Start engine and turn AC to maximum cold with fan on high
• Allow system to run for 5-10 minutes and verify cold air output from vents
• Monitor AC pressures: low side should be approximately 25-35 PSI, high side 175-250 PSI at idle with ambient temperature 70-90°F
• Check all connections for refrigerant leaks using electronic leak detector or soap solution
• Verify compressor clutch engages and disengages properly
• Observe temperature drop across evaporator: vent temperature should be 35-45°F colder than ambient
• Listen for abnormal hissing or restriction noise at expansion valve location
• Verify no frost accumulation on suction line (would indicate overcharge or restriction)
• Test system operation through several on/off cycles

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