AC Compressor Oil Add

This procedure adds the correct amount of refrigerant oil to the AC compressor on a 1970 AMC Rebel Machine with 390ci V8 engine to ensure proper lubrication and system performance.

Warnings

Tools required

Parts

• R12 compatible refrigerant oil (mineral oil) × 1 — Use manufacturer-approved R12 mineral oil

Fluids

• R12 compatible refrigerant oil — 0.25 qt

Preparation

1. Park vehicle on level surface and set parking brake
2. Allow engine to cool completely if recently operated
3. Verify the type of refrigerant oil compatible with your system (original R12 systems use mineral oil)
4. Have refrigerant recovery equipment ready and verified operational
5. Locate AC compressor on passenger side of engine, driven by belt from crankshaft

Procedure

1. 1

   Recover existing refrigerant
   Connect AC manifold gauges to the high and low side service ports. Use EPA-approved refrigerant recovery machine to completely evacuate all R12 refrigerant from the system. Record the amount of refrigerant recovered for recharging.
2. 2

   Remove compressor inlet line
   Using appropriate wrench, disconnect the suction line fitting from the compressor inlet port. This is typically the larger of the two lines. Have a clean container ready to catch any oil that drains out. Measure and record the amount of oil that drains.
3. 3

   Drain old oil from compressor
   Slowly rotate the compressor clutch hub by hand several complete revolutions to pump out remaining oil through the open suction port. Drain into a clean graduated container and measure the total oil removed. This measurement determines how much fresh oil to add.
4. 4

   Calculate oil quantity needed
   Total system capacity for the York or Tecumseh compressor used in 1970 AMC systems is typically 10-11 ounces. Add the same amount of fresh oil as was removed, or if uncertain, add 6-8 ounces for a complete system service.
5. 5

   Inject new refrigerant oil
   Using a graduated oil injector, slowly pour the measured amount of fresh R12-compatible mineral oil into the compressor suction port. Rotate the clutch hub by hand several times to distribute oil internally through the compressor.
6. 6

   Reconnect suction line
   Inspect the suction line fitting and O-ring for damage or deterioration. Replace O-ring if necessary. Reconnect the suction line to the compressor inlet port and tighten securely by hand, then snug with wrench. Do not overtighten aluminum fittings.
7. 7

   Evacuate system
   Use a vacuum pump connected to the manifold gauges to evacuate the system to at least 29 inches of mercury vacuum. Hold vacuum for minimum 30 minutes to ensure system is leak-free and all moisture is removed.
8. 8

   Recharge with refrigerant
   Recharge the system with the same amount of R12 refrigerant that was recovered, or per factory specification (typically 3 to 3.5 pounds for this application). Monitor gauges during charging to ensure proper pressures.

Reassembly

1. Verify all AC line connections are tight and secure
2. Check compressor drive belt tension and adjust if necessary
3. Ensure no tools or materials are left in engine compartment

Verification

• Start engine and turn AC to maximum cold with blower on high
• Compressor clutch should engage and disengage normally without unusual noise
• Check manifold gauge readings: low side should be 25-35 psi, high side 180-250 psi at idle with ambient temperature around 70-80°F
• Verify cold air output from dash vents
• Inspect all connections for signs of oil leakage
• Use leak detector to verify no refrigerant leaks at service ports or compressor fittings
• Allow system to run for 10-15 minutes and recheck pressures to ensure stable operation

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