AC Recharge

This procedure evacuates the existing refrigerant from the AC system, checks for leaks, and recharges it with the correct amount of R-134a refrigerant and PAG oil to restore proper air conditioning function.

Warnings

Tools required

Parts

• R-134a refrigerant × 1 — 1.75 lbs total system capacity
• PAG 46 compressor oil × 1 — Motorcraft YN-12-C or equivalent
• UV dye (if not already in system) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and set parking brake
2. Turn engine off and allow AC system to cool for at least 30 minutes
3. Locate the low-pressure service port on the larger diameter AC line near the accumulator on the passenger side of the engine bay
4. Locate the high-pressure service port on the smaller diameter line near the condenser
5. Verify you have the correct amount of refrigerant: 2015-2020 F-150 5.0L V8 requires 1.75 lbs (28 oz) of R-134a
6. Set up AC recovery machine and manifold gauge set according to manufacturer instructions

Procedure

1. 1

   Connect recovery equipment and remove existing refrigerant
   Connect the manifold gauge set to both the low-pressure (blue) and high-pressure (red) service ports. Remove caps from service ports and attach fittings hand-tight, then snug with a wrench. Connect the yellow hose from the manifold to the recovery machine. Start the recovery machine and follow its prompts to recover all refrigerant from the system. This typically takes 5-15 minutes depending on the amount of refrigerant present. Recovery is complete when both gauges read zero and machine indicates completion.
2. 2

   Perform vacuum test
   Connect the yellow center hose from the manifold gauge set to the vacuum pump. Open both the low-side (blue) and high-side (red) valves on the manifold. Start the vacuum pump and pull a vacuum on the system. The gauges should read at least 29 inches of mercury (approximately -30 psi). Continue vacuuming for a minimum of 30 minutes to remove all moisture and air from the system. For best results, vacuum for 45 minutes.
3. 3

   Check for system leaks
   After vacuuming for 30-45 minutes, close both manifold valves (blue and red) and turn off the vacuum pump. Monitor the gauges for 10 minutes. The vacuum should hold steady at 29 inches Hg. If the vacuum rises (pressure increases toward zero), there is a leak in the system that must be repaired before proceeding. If vacuum holds steady, proceed to charging.
4. 4

   Add compressor oil if needed
   Determine if compressor oil needs to be added. If you recovered less than 1 oz of oil during recovery, or if any components were replaced, add the appropriate amount of PAG 46 oil. For a simple recharge with no component replacement, add 1-2 oz of oil. Oil can be added through the low-side service port using an oil injector tool. If significant oil was recovered, do not add additional oil.
5. 5

   Prepare refrigerant charging setup
   Disconnect the vacuum pump and connect the yellow center hose to the refrigerant supply. If using a charging cylinder, place it on the electronic scale and tare the scale to zero. If using individual cans, prepare the first can with a dispensing valve. Add UV dye to the refrigerant supply if the system does not already contain dye (most factory systems already have dye).
6. 6

   Charge refrigerant through low-side port
   With the engine off, open the low-side (blue) valve on the manifold to allow refrigerant to flow into the system. Add approximately 14 oz (half the total capacity) with the engine off. The low-side gauge should rise to 40-60 psi. Close the low-side valve once 14 oz has been added.
7. 7

   Start engine and complete charging
   Start the engine and turn the AC to MAX with the blower on high speed. Allow the engine to idle at approximately 1500 RPM. Open the low-side (blue) valve on the manifold and continue adding refrigerant slowly through the low-side port only. Never charge through the high-side while the compressor is running. Add refrigerant until the total amount reaches 28 oz (1.75 lbs). Monitor the low-side gauge: it should read 25-45 psi depending on ambient temperature. High-side pressure should read 150-250 psi depending on ambient temperature.
8. 8

   Monitor system pressures
   With the system fully charged and running at 1500 RPM with MAX AC, verify proper operation. At 70-80°F ambient temperature, low-side pressure should be 25-35 psi and high-side should be 150-200 psi. At 90-100°F ambient, low-side should be 35-45 psi and high-side 200-250 psi. Pressures outside these ranges indicate possible issues with airflow, compressor function, or expansion valve operation.
9. 9

   Disconnect equipment and check for leaks
   Once charging is complete and pressures are verified, close all manifold valves. Turn off the engine and AC. Carefully disconnect the manifold gauge hoses from both service ports, working quickly to minimize refrigerant loss. Reinstall the plastic caps on both service ports. Use a leak detector or UV light to check all connections, service ports, and visible AC lines for leaks. Pay special attention to the compressor shaft seal and line fittings.

Reassembly

1. Ensure service port caps are securely installed on both low and high-side ports
2. Store all AC service equipment properly and ensure recovery tank is labeled with refrigerant type
3. Wipe down any oil residue from service port areas

Verification

• Start the engine and turn AC to MAX with recirculation on and blower at high speed
• Allow system to run for 5 minutes, then measure vent temperature with a thermometer. Vent temp should be 38-45°F at idle with 70-80°F ambient temperature
• Verify compressor clutch engages and disengages normally without unusual noise or vibration
• Check that both AC lines at the firewall show appropriate temperature difference: low-pressure line (larger) should be cold to touch, high-pressure line (smaller) should be warm to hot
• Listen for proper compressor operation without excessive noise, grinding, or squealing
• Verify cooling performance improves as engine RPM increases from idle to 2000 RPM
• Recheck service port areas for leaks after 24 hours of operation if possible

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