A/C System Leak Tests

Testing the refrigerant system for leaks is one of the most important phases of troubleshooting. Several types of leak detectors are available that are suitable for detecting A/C system leaks. One or more of the following procedures will prove useful for detecting leaks and checking connections after service work has been performed. Prior to performing any leak test, prepare the vehicle as follows:
1. Attach a suitable gauge manifold to system and observe pressure readings.
2. If little or no pressure is indicated, the system must be partially charged.
3. If gauges indicate pressure, set engine to run at fast idle and operate system at maximum cooling for 10-15 minutes, then stop engine and perform leak tests.

FLAME TYPE (HALIDE) LEAK DETECTORS
Avoid inhaling fumes produced by burning refrigerant when using flame-type detectors. Use caution when using detector near flammable materials such as interior trim components. Do not use flame-type detector where concentrations of combustible or explosive gasses, dusts or vapors may exist.
1. Light leak detector and adjust flame as low as possible to obtain maximum sensitivity.
2. Allow detector to warm until copper element is cherry-red. Flame should be almost colorless.
3. Test reaction plate sensitivity by passing end of sensor hose near an opened can of refrigerant. Flame should react violently, turning bright blue.
4. If flame does not change color, replace reaction plate following manufacturer's instructions.
5. Allow flame to clear, then slowly move sensor hose along areas suspected of leakage while observing flame. Position sensor hose under areas of suspected leakage, as R-12 refrigerant is heavier than air.
6. Move sensor hose under all lines, fittings and components. Insert hose into evaporator case, if possible, and check compressor shaft seal.
7. The presence of refrigerant will cause flame to change color as follows: Pale blue, no refrigerant; yellow-yellow/green, slight leak; bright blue-purple/blue, major leak or concentration of refrigerant.
8. If detector indicates a large leak or heavy concentration of refrigerant, ventilate area using a small fan in order to pinpoint leak.
9. Repair leaks as needed, evacuate and recharge system, then recheck system for leaks.

ELECTRONIC LEAK DETECTORS
The procedure for using an electronic leak detector is similar to the procedure for flame-type leak detectors, except that the presence of refrigerant is indicated by an audible tone or flashing light. Refer to operating instructions for unit being used, and observe the following procedures:
1. Move detector probe 1 inch per second along areas of suspected leakage.
2. Position probe under area to be tested as refrigerant is heavier than air.
3. Check gauge manifold, hoses and service ports for leakage.

FLUID LEAK DETECTORS
Apply leak detector solution around joints to be tested. A cluster of bubbles will form immediately if there is a leak. A white foam that forms after a short while will indicate an extremely small leak. In some confined areas such as sections of the evaporator and condenser, electronic leak detectors will be more useful.