AC Expansion Valve (TXV)

This procedure covers the removal and replacement of the AC expansion valve (TXV) on a 2007 Ram 3500 with 5.9L Cummins diesel engine, requiring recovery and recharge of the AC system.

Warnings

Tools required

Parts

• AC expansion valve (TXV) × 1 — Use OEM Mopar or quality aftermarket specific to 5.9L Cummins application
• AC line O-rings (various sizes) × 1 — Replace all disturbed O-rings
• PAG 46 refrigerant oil × 1 — 50-80ml depending on system loss
• UV leak detection dye (optional) × 1 — R-134a compatible if not already in system

Fluids

• R-134a refrigerant

Preparation

1. Park vehicle on level surface and set parking brake
2. Allow engine to cool completely if recently operated
3. Disconnect negative battery terminal to prevent accidental fan activation
4. Verify AC system contains refrigerant by checking static pressure (should be 60-90 PSI at ambient temperature)
5. Connect AC recovery machine and completely recover all refrigerant per EPA guidelines, noting the amount recovered
6. Relieve any residual pressure in the system after recovery
7. Locate the expansion valve at the firewall on the evaporator inlet line (passenger side near the firewall)
8. Clean the work area around AC fittings to prevent dirt ingress

Procedure

1. 1

   Remove engine cover and gain access
   Remove the plastic engine cover by pulling upward on the retaining clips. This provides better access to the AC lines at the firewall. On some configurations, you may need to remove the air intake duct for improved access to the passenger side firewall area.
2. 2

   Disconnect AC lines from expansion valve
   Locate the expansion valve at the firewall where the liquid line and evaporator inlet meet. Using appropriate wrenches, disconnect the liquid line fitting from the inlet side of the expansion valve. Then disconnect the evaporator line from the outlet side. Cap or plug both lines immediately to prevent moisture and debris entry. Note the orientation of the expansion valve for proper replacement.
3. 3

   Remove expansion valve mounting
   The expansion valve is typically secured with a bracket or clips at the firewall. Remove any retaining hardware securing the valve to its mounting bracket. Carefully extract the expansion valve from the evaporator inlet connection, noting the presence of an internal screen filter on some models.
4. 4

   Inspect and remove old O-rings
   Remove all old O-rings from the AC line fittings and expansion valve ports. Inspect the mating surfaces on both the lines and new expansion valve for damage, corrosion, or debris. Clean mating surfaces with a lint-free cloth. Check that any internal screen filter (if equipped) is clean or replace if clogged.
5. 5

   Install new O-rings
   Install new O-rings on all AC line connections. Lubricate each O-ring lightly with clean refrigerant oil (PAG 46) before installation. Ensure O-rings are seated properly in their grooves and not twisted or pinched. Do not reuse old O-rings as they lose elasticity and sealing ability.
6. 6

   Install new expansion valve
   Remove the new expansion valve from its sealed packaging immediately before installation. Confirm the replacement valve matches the original (this platform commonly uses a block/H-valve type with an internal sensing element). Install the expansion valve into the evaporator connection at the firewall in the same orientation as the original, observing any inlet/outlet or flow markings if present. Secure any mounting brackets or clips.
7. 7

   Reconnect AC lines
   If the valve uses a block/H-valve design, connect the line plate to the valve and torque the retaining bolt to specification (typically ~7-9 ft-lbs / 80-100 in-lbs). For threaded fittings, hand-start first for proper thread engagement, then torque to the manufacturer's spec; do not overtighten aluminum fittings. Do not overtighten aluminum fittings. Connect the evaporator outlet line in the same manner. Use two wrenches (one to hold, one to turn) to prevent twisting the lines or valve body.
8. 8

   Add refrigerant oil
   Add the appropriate amount of PAG 46 refrigerant oil to compensate for oil lost during recovery. Typically add approximately 1 oz (~30ml) to replace the small amount of oil lost during recovery, or match the amount of oil recovered from the machine. If the system was completely evacuated or significant oil was recovered, consult service specifications for total system capacity. Oil can be injected through the low-side service port or added directly to the compressor.
9. 9

   Vacuum test the system
   Connect the AC manifold gauges to the service ports. Connect a vacuum pump to the center port and evacuate the system to at least 29.5 inHg vacuum. Maintain vacuum for a minimum of 30 minutes (45 minutes recommended for this system size). Close the manifold valves and shut off the vacuum pump. Monitor the vacuum gauge for 10 minutes; vacuum should hold steady indicating no leaks.
10. 10

    Recharge the AC system
    Using the AC recovery/recharge machine or manifold gauges with refrigerant scale, charge the system with R-134a refrigerant to the specified capacity (typically 28-32 oz for single-evaporator systems, more for rear-AC equipped models; verify exact charge on the underhood label). Charge through the low-side port with the engine off, or follow machine instructions. Add UV dye if desired for future leak detection. Do not overcharge the system.
11. 11

    Leak test all connections
    With the system charged to operating pressure, spray all disturbed connections with soap solution or use an electronic leak detector. Check the expansion valve connections, service ports, and any other fittings touched during the repair. Look for bubbles indicating leaks. If using UV dye, operate the system for 10 minutes then check with UV light.

Reassembly

1. Reinstall the air intake duct if removed, ensuring all clamps are properly tightened
2. Reinstall the engine cover by pressing down on the mounting clips until they click into place
3. Reconnect the negative battery terminal
4. Wipe down any refrigerant oil spills on engine components

Verification

• Start the engine and turn AC to maximum cool with fan on high
• Allow the system to run for 5-10 minutes to reach operating temperature
• Check that both AC lines at the expansion valve show appropriate temperature differential (inlet should be warm, outlet should be cold)
• Verify center dash vents blow cold air (typically 38-45°F with 80-90°F ambient)
• Check AC pressures with manifold gauges: low side should be 25-45 PSI, high side 175-250 PSI at idle (varies with ambient temperature)
• Listen for unusual noises from the compressor or expansion valve area
• Verify no refrigerant odor or frost accumulation at connections indicating leaks
• Confirm the compressor cycles on and off appropriately as system reaches temperature
• Recheck all connections for leaks after system reaches full operating temperature

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