This procedure adds the correct amount of PAG oil to the AC compressor system to ensure proper lubrication and longevity of the compressor after service or replacement.

Warnings

Tools required

Parts

• AC line O-rings × 4 — Use OEM specification
• R-134a refrigerant × 1 — Motorcraft YN-19

Fluids

• PAG 46 compressor oil — 0.25 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure engine is cool to the touch before beginning work
3. Verify the AC system refrigerant type is R-134a (label on hood or radiator support)
4. Note the total system refrigerant capacity from underhood label (typically 1.43-1.52 lbs for 2015-2020 F-150)
5. Determine reason for oil addition (compressor replacement, line replacement, or suspected low oil)
6. If compressor was replaced, drain and measure oil from old compressor to determine amount lost

Procedure

1. 1

   Recover refrigerant from system
   Connect AC recovery machine to both high and low side service ports. Follow recovery machine instructions to completely evacuate all R-134a refrigerant from the system. Record the amount of refrigerant recovered for recharge reference. Allow system to equalize to atmospheric pressure.
2. 2

   Determine correct oil quantity
   For new compressor installation, drain oil from new compressor into graduated container and measure (typically 8-10 oz pre-filled). Add back manufacturer-specified amount (typically 7 oz total system capacity). If adding oil due to component replacement: suction line = 2 oz, liquid line = 1 oz, condenser = 1 oz, evaporator = 3 oz. If topping off without component replacement, add no more than 1-2 oz.
3. 3

   Access compressor discharge line
   Locate the AC compressor on the passenger side of the engine below the alternator. Identify the discharge line (smaller diameter, high-pressure line) connected to the top of the compressor. Clean area around the fitting to prevent contamination.
4. 4

   Disconnect discharge line
   Using appropriate wrench, loosen and remove the discharge line fitting from the compressor. Remove and discard the old O-rings from both the line and compressor port. Cap or plug the open line and compressor port immediately to prevent moisture and debris entry.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
5. 5

   Add PAG oil to system
   Using PAG oil injector tool, inject the calculated amount of PAG 46 oil directly into the compressor discharge port. Pour slowly to allow oil to settle into the compressor. Alternatively, oil can be added through the suction port or by pouring directly into the compressor before line reconnection.
6. 6

   Install new O-rings
   Install new O-rings onto the discharge line fitting. Lightly coat O-rings with fresh PAG 46 oil to aid installation and ensure proper seal. Inspect compressor port for any debris or damage before reconnection.
7. 7

   Reconnect discharge line
   Remove caps from compressor port and discharge line. Carefully align and thread the discharge line fitting onto the compressor by hand to avoid cross-threading. Torque to specification using torque wrench.
   Torque spec

   AC Line Fittings20 Nm (15 lb-ft)
8. 8

   Rotate compressor clutch
   Manually rotate the compressor clutch 10-15 revolutions by hand to distribute the added oil throughout the compressor internals. This prevents oil slugging when the compressor first starts. Rotation should be smooth without binding.
9. 9

   Vacuum system
   Connect AC vacuum pump to service ports. Evacuate system to 29+ inches Hg (mercury) vacuum and hold for minimum 30-45 minutes. This removes all air and moisture. Monitor vacuum gauge for vacuum decay which indicates a leak. System should hold steady vacuum.
10. 10

    Recharge AC system
    Using AC manifold gauges or charging machine, add the recorded amount of R-134a refrigerant (or spec amount from underhood label if different). Charge through low-side port only with engine running and AC on MAX/recirculate. Monitor pressures: low side should be 25-45 psi, high side 150-250 psi at 75°F ambient.

Reassembly

1. Verify all AC line fittings are properly torqued and no caps or plugs were left in the system
2. Ensure compressor clutch gap is correct (0.014-0.026 inches) and clutch engages when AC is activated
3. Check drive belt tension and condition after compressor service

Verification

• Start engine and turn AC to MAX cold with fan on high. Compressor clutch should engage within 5-10 seconds
• Verify cold air output from vents (typically 38-45°F at vents with 75°F ambient temperature)
• Monitor AC pressures: low side 25-45 psi, high side 150-250 psi at idle with 75°F ambient
• Check all AC line connections for refrigerant leaks using electronic leak detector or soap solution
• Listen for unusual compressor noises which could indicate insufficient oil or internal damage
• Test AC performance after 10-15 minutes of operation to ensure consistent cooling

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