Whenever a refrigerant leak is suspected, begin by checking for leaks at the fitting or valves. There are several methods of detecting leaks in the air conditioning system; among them the two most popular are (1) halide leak detection or the "open flame method'', and (2) electronic leak-detection. Use of an electronic leak detector, if available, is preferable for ease and safety of operation.
The halide leak detector is a torch-like device which produces a yellow-green color when refrigerant is introduced into the flame at the burner. A purple or violet color indicates large amounts of refrigerant at the burner.
An electronic leak detector is a small portable electronic device with an extended probe. With the unit activated the probe is passed along those components of the system which contain refrigerant. If a leak is detected, the unit will sound an alarm signal or activate a display signal depending on the manufacturer's design. Follow the manufacturer's instructions carefully. Move the probe at approximately 1 in. (25mm) per second around the suspected leak area. When escaping refrigerant gas is located, the ticking or beeping signal from the detector will increase in beeps per second. If the gas is relatively concentrated, the signal will be a constant shrill.
CAUTION
Care should be taken to operate either type of detector in well ventilated areas,
so as to reduce the chance of personal injury, which may result from coming
in contact with the poisonous gases produced when R–12 is exposed to flame
or electric spark.
If a tester is not available, perform a visual inspection and apply a soap and water solution to the questionable area or fitting. Bubbles will form to indicate a leak. Make sure to rinse the solution from the area before making repairs.