AC Leak Detection and Charging
Finding leaks, recovering, weighing and recharging correctly.
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Safety notice
- Refrigerant handling requires certification and approved equipment. Never vent refrigerant to atmosphere, never open a pressurised system, and never add sealant as a shortcut for a proper repair.
What you will learn
- Find refrigerant leaks
- Explain recovery and recharge
- Follow safe refrigerant handling
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Refrigerant does not get “used up”; if the charge is low, it escaped. That is why diagnosis always includes a leak test rather than a simple top-up. Electronic detectors and UV dye locate leaks at joints, condensers, evaporators and service ports.
Correct recharging means recovering the old charge, evacuating with a vacuum pump to remove moisture and air, then weighing in the exact charge and oil the manufacturer specifies. Guessing the charge, or skipping the vacuum, causes poor cooling and premature failure.
- Confirm the complaint and measure vent temperature.
- Check clutch engagement and read high/low side pressures.
- Leak-test with an electronic detector or UV dye.
- Recover, evacuate and weigh in the correct charge and oil.
- Verify vent temperature and pressures at a known ambient temperature.
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CASE 016
AC Cold on the Motorway, Warm in Traffic
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The air conditioning blows cold when driving but warm when the car is stationary in traffic. The compressor clutch engages normally.
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Key points
- Low refrigerant means a leak — find it.
- Evacuate before charging to remove moisture and air.
- Weigh the charge; the amount is manufacturer specific.
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Key points
- Refrigerant does not wear out — if it is low, it leaked
- Leak-test before recharging
- Weigh the charge; never guess
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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