This procedure evacuates, vacuum tests, and recharges the AC system on a 2014 Ram 2500 with the 6.7L Cummins diesel engine to restore proper cooling performance.

Warnings

Tools required

Parts

• R-134a Refrigerant × 1 — Use OEM specification
• PAG 46 or PAG 100 Compressor Oil × 1 — Mopar or equivalent
• AC System O-ring Kit × 1 — Use if any fittings are disturbed

Preparation

1. Park vehicle on level surface and set parking brake
2. Start engine and turn AC to MAX COOL with blower on HIGH for 2 minutes to assess current system performance
3. Turn off engine and allow to cool if performing leak inspection
4. Verify AC system contains R-134a refrigerant using identifier tool if available
5. Locate low-side service port (larger port, typically on accumulator/drier near firewall) and high-side service port (smaller port, typically on liquid line near condenser)
6. Clean service port caps and surrounding area to prevent contamination

Procedure

1. 1

   Connect recovery machine and recover existing refrigerant
   Remove caps from both high and low-side service ports. Connect AC recovery machine hoses to both ports with low-side (blue) to larger port and high-side (red) to smaller port. Follow recovery machine instructions to evacuate all refrigerant from the system. Record the amount of refrigerant and oil recovered. If significantly low (less than 50% capacity), inspect for leaks before recharging.
2. 2

   Perform visual leak inspection
   With system evacuated, visually inspect all AC line connections, compressor shaft seal, condenser, evaporator drain area, and service ports for signs of oil residue or damage. Pay special attention to line fittings at the compressor, condenser, and firewall pass-through areas on this vehicle. Note any areas requiring repair before proceeding.
3. 3

   Vacuum test the system
   Ensure all service port valves on manifold gauge or machine are closed. Start vacuum pump or activate vacuum cycle on AC machine. Pull vacuum to at least 29 inches Hg (98 kPa). Continue vacuum for minimum 30 minutes, 45 minutes preferred for this system size. Monitor vacuum gauge throughout process.
4. 4

   Perform vacuum hold test
   After vacuum period, close valve to vacuum pump and observe gauge for 10-15 minutes. Vacuum should hold steady at 29 inches Hg. If vacuum drops more than 2 inches Hg, system has a leak that must be repaired before charging. If vacuum holds, proceed to charging.
5. 5

   Add compressor oil if needed
   Calculate oil requirement: if more than 1 oz of oil was recovered, add same amount of fresh PAG oil to system. For the 6.7L Cummins application, use PAG 46 viscosity oil. If system was opened for component replacement, add oil per component specifications. Add oil through low-side port using oil injector tool before refrigerant charge.
6. 6

   Charge system with R-134a refrigerant
   With engine OFF, begin charging through low-side port only. The 2014 Ram 2500 6.7L Cummins 4WD requires approximately 42-46 oz (1190-1304 grams) of R-134a - verify exact specification on underhood AC label. Charge slowly to prevent liquid slugging. Add approximately 80% of total charge with engine off.
7. 7

   Complete charge with engine running
   Start engine and turn AC to MAX COOL with blower on HIGH. Allow compressor to engage. Continue adding remaining refrigerant through LOW-SIDE PORT ONLY while monitoring gauges. Target pressures at 80°F ambient: Low side 25-35 psi, High side 225-250 psi. Stop when correct weight of refrigerant is added per label specification.
8. 8

   Monitor system pressures and operation
   With system fully charged and running at MAX COOL, observe both gauges for 5 minutes. Low-side should remain steady 25-40 psi depending on ambient temperature. High-side should be 200-275 psi depending on ambient. Compressor should cycle normally. Listen for unusual noises from compressor.
9. 9

   Perform leak detection
   With system pressurized and running, use electronic leak detector to check all fittings, compressor seal, condenser, and service ports. Pay special attention to any areas that showed oil residue during visual inspection. If leak is detected, system must be recovered and leak repaired before final charge.
10. 10

    Disconnect equipment and secure system
    Turn off engine and AC. Carefully disconnect manifold gauges or machine hoses from service ports - expect small amount of refrigerant release. Immediately install service port caps hand-tight to prevent contamination and moisture entry. Wipe any residual oil from connection points.

Reassembly

1. Ensure both high and low-side service port caps are securely installed
2. Clean any oil residue from engine bay components
3. Document the amount of refrigerant and oil added for service records

Verification

• Start engine and run AC on MAX COOL with blower on HIGH for 5 minutes
• Measure center vent temperature with infrared thermometer - should be 38-42°F at 75°F ambient, colder at higher ambient temperatures
• Verify compressor clutch engages and disengages normally without unusual noise
• Check that condenser fans activate when AC is on and high-side pressure increases
• Confirm no refrigerant odor or visible oil leaks around service ports and fittings
• Test AC performance at idle and 1500 RPM - should produce consistently cold air
• Verify blower motor operates at all speeds without issue

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