AC Recharge

This procedure evacuates residual refrigerant from the factory A/C system, checks for leaks, and recharges with R-12 refrigerant to original specifications for the 1970 AMC Rebel Machine.

Warnings

Tools required

Parts

• R-12 refrigerant × 1 — Use period-correct R-12 or convert to R-134a with retrofit kit
• PAG oil for compressor × 1 — Use mineral oil for R-12 systems
• A/C service valve caps × 2 — Standard 1/4 inch caps

Preparation

1. Ensure engine is off and has been sitting for at least 30 minutes to equalize system pressure
2. Verify A/C compressor clutch engages when system is activated (if refrigerant is present)
3. Inspect all visible A/C lines, condenser, and evaporator housing for obvious damage or oil residue indicating leaks
4. Locate high-side and low-side service ports on the A/C system (low-side typically on accumulator or large line near firewall, high-side on liquid line near condenser)
5. Have vehicle in well-ventilated area or shop with adequate airflow

Procedure

1. 1

   Connect manifold gauges
   Remove caps from high-side and low-side service ports. Connect blue hose from manifold gauge set to low-side port (larger diameter) and red hose to high-side port (smaller diameter). Ensure connections are tight to prevent refrigerant escape. Note initial system pressures if any refrigerant remains in system.
2. 2

   Recover existing refrigerant
   Connect center manifold hose to R-12 recovery machine. Start recovery machine and open both high and low side valves on manifold gauge set. Allow machine to recover all refrigerant from system until gauges read zero or vacuum. This typically takes 10-15 minutes. Close manifold valves and recovery machine when complete.
   ⚠If system shows zero pressure before recovery, there is a leak that must be repaired before recharging.
3. 3

   Perform vacuum test
   Connect center manifold hose to vacuum pump. Open both manifold valves and start vacuum pump. Evacuate system to 29-30 inches of mercury (Hg) vacuum. Continue evacuating for minimum 30 minutes to remove all moisture and air from system. Close both manifold valves and turn off vacuum pump.
4. 4

   Check system for leaks
   Monitor vacuum gauge for 15 minutes with pump off and valves closed. Vacuum should hold steady at 29-30 inches Hg. If vacuum drops more than 2 inches, there is a leak in the system that must be located and repaired before proceeding. If vacuum holds, system is sealed and ready for recharge.
   ℹ️A slow vacuum loss may indicate moisture in system. Re-evacuate for another 30 minutes if needed.
5. 5

   Prepare refrigerant charge
   The 1970 AMC Rebel Machine with factory A/C requires approximately 3.0 pounds (48 ounces) of R-12 refrigerant. Connect refrigerant canister or tank to center manifold hose. If adding compressor oil, add 2-4 ounces of mineral oil appropriate for R-12 systems through low-side port before refrigerant charge.
6. 6

   Charge system with liquid refrigerant
   With engine off, open valve on refrigerant container. Slowly open low-side manifold valve (blue gauge side) and allow liquid refrigerant to flow into system. Invert refrigerant can if using disposable cans to charge with liquid. Add approximately 2.5 pounds of refrigerant through low side with engine off. Watch low-side gauge rise to approximately 70-90 PSI at ambient temperature.
7. 7

   Complete charge with engine running
   Start engine and set A/C controls to MAX with blower on high. Set engine to fast idle (1200-1500 RPM). The compressor clutch should engage. Open low-side valve and add remaining refrigerant in vapor form (can upright) until low-side pressure reads 25-35 PSI and high-side pressure reads 200-250 PSI with ambient temperature 70-80°F. Adjust charge amount based on ambient temperature.
   ⚠Never add liquid refrigerant through low side with compressor running as this can damage the compressor.
8. 8

   Verify system operation
   With engine at fast idle and A/C on MAX, verify compressor clutch cycles properly or remains engaged. Check center dashboard vents for cold air output (40-50°F with 80°F ambient). High-side pressure should be 200-250 PSI and low-side 25-35 PSI at 1500 RPM with 70-80°F ambient. Adjust pressures as needed for ambient temperature.
9. 9

   Check for leaks
   With system running, use electronic leak detector to check all fittings, service ports, compressor shaft seal, condenser, and line connections. Pay special attention to service port connections just used. If leaks detected, recover refrigerant, repair leak, and repeat procedure.
10. 10

    Disconnect gauges and finish
    Turn off engine and A/C. Close both manifold gauge valves. Quickly disconnect gauge hoses from service ports (small amount of refrigerant will escape). Immediately install service port caps finger-tight, then snug with wrench. Wipe any oil residue from connections.

Reassembly

1. Ensure both service port caps are installed securely to prevent refrigerant loss and contamination
2. Clean any refrigerant oil residue from engine bay components
3. Document the amount of refrigerant and oil added for future service reference

Verification

• Start engine and run A/C on MAX with blower on high for 5 minutes
• Verify center vent temperature is 40-50°F with 70-80°F ambient temperature (temperatures will vary with ambient)
• Confirm compressor clutch engages and cycles properly without unusual noises
• Check that condenser fan operates when A/C is on
• Verify no refrigerant odor or oil residue around service ports or connections
• Test A/C performance during short test drive to ensure adequate cooling under load

More procedures for this vehicle