AC Recharge

Evacuate and recharge the air conditioning system with R-134a refrigerant to restore proper cooling performance.

Warnings

Tools required

Parts

• PAG oil (if system was opened) × 1 — Use OEM specification for compressor type

Fluids

• R-134a

Preparation

1. Park vehicle on level surface and apply parking brake
2. Turn ignition off and remove key
3. Allow engine to cool completely if recently operated
4. Verify AC compressor clutch is not seized by rotating center hub by hand (engine off)

Procedure

1. 1

   Locate AC service ports
   Open hood and locate the AC service ports on the refrigerant lines. The low-pressure port is on the larger diameter suction line (between evaporator and compressor) with a blue or black cap. The high-pressure port is on the smaller diameter liquid line (between condenser and evaporator) with a red cap. On the 2008 Viper, these are typically accessible near the firewall on the passenger side of the engine bay.
2. 2

   Connect recovery machine
   Remove caps from both AC service ports. Connect the manifold gauge set: blue hose to low-pressure port, red hose to high-pressure port. Connect the yellow center hose to the refrigerant recovery machine. Record the ambient temperature for later reference when determining proper system charge.
3. 3

   Recover existing refrigerant
   Start the recovery machine and follow manufacturer instructions to evacuate all refrigerant from the system. The machine will indicate when recovery is complete (typically when pressures equalize near vacuum and no additional refrigerant is recovered for several minutes). Note the amount of refrigerant recovered on the machine's scale for comparison to specifications.
4. 4

   Inspect system for leaks
   With the system evacuated, visually inspect all accessible AC lines, connections, condenser, and compressor for signs of oil residue or damage. If the system was significantly low on refrigerant, use an electronic leak detector or UV dye inspection (if previously added) to locate any leaks. Address any leaks before proceeding with recharge.
5. 5

   Evacuate system with vacuum pump
   Connect the yellow hose from the manifold gauge set to the vacuum pump. Open both manifold valves (high and low side). Start the vacuum pump and evacuate the system to at least 29 inches of mercury vacuum. Continue vacuum for a minimum of 30 minutes to remove all moisture and air from the system. This step is critical for proper AC performance and compressor longevity.
6. 6

   Perform vacuum hold test
   After 30 minutes of vacuum, close both manifold valves and shut off the vacuum pump. Observe the vacuum gauge for 10 minutes. The vacuum should hold steady at 29 inches of mercury or higher. If vacuum drops more than 2 inches, there is a leak in the system that must be repaired before charging. If vacuum holds, proceed to charging.
7. 7

   Prepare refrigerant supply
   Close both manifold valves. Disconnect the yellow hose from the vacuum pump. Connect the yellow hose to the R-134a refrigerant supply (either bulk tank or charging cylinder). Place the refrigerant container on the scale and record the starting weight. The 2008 Viper 8.4L V10 AC system capacity should be confirmed from the factory service manual / underhood AC label before charging (AI estimate ~2.25 pounds of R-134a is unverified).
8. 8

   Charge system via low-pressure side
   With engine off, open the low-pressure valve (blue side) on the manifold gauge set. Invert the refrigerant container if using small cans, or follow bulk tank procedures. Allow liquid refrigerant to flow into the system until approximately two-thirds of the factory-specified total charge has entered (monitor on scale). Do not charge liquid through the high-pressure side with engine off.
9. 9

   Complete charging with engine running
   Start the engine and turn AC to MAX cool with blower on high. Maintain engine speed at approximately 1500 RPM. Continue charging through the low-pressure side only, adding refrigerant vapor (keep container upright) until the total charge reaches the factory-specified refrigerant capacity. Monitor gauges against factory-specified pressures for this vehicle; typical R-134a values are approximately low side 25-45 PSI and high side 200-250 PSI at 1500 RPM with ambient around 70-80°F, but confirm targets against the service manual/pressure-temperature chart. Adjust charge as needed based on gauge readings and vent temperature.
10. 10

    Verify system operation
    With engine running at 1500 RPM and AC on MAX, verify AC compressor clutch is engaged. Check that both AC lines show appropriate temperature differential: suction line (low pressure) should be cold to touch, discharge line (high pressure) should be warm to hot. Insert thermometer in center dash vent; temperature should be 35-45°F with ambient temperature around 75°F. This system does not use a sight glass; verify charge by weight and by monitoring high/low side pressures and vent temperature rather than visual refrigerant appearance.
11. 11

    Disconnect equipment and secure system
    Turn off AC and engine. Close both manifold valves. Quickly disconnect the blue hose from the low-pressure port first, then the red hose from the high-pressure port to minimize refrigerant loss. Immediately reinstall the service port caps on both ports, tightening by hand. Remove manifold gauge set and store equipment.

Reassembly

1. Reinstall service port caps securely on both low and high-pressure ports
2. Ensure no tools or equipment remain in engine bay
3. Close hood

Verification

• Start engine and turn AC to MAX cool with blower on high
• Verify AC compressor clutch engages within 5 seconds
• Check center dash vent temperature reaches 35-45°F within 2-3 minutes
• Listen for unusual noises from compressor or AC system
• Verify no refrigerant odor or visible leaks at service ports
• Test AC performance during short test drive to confirm consistent cooling

More procedures for this vehicle