Leak Detectors

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Fig 1: Identifying Typical Leak Detector

Courtesy of BMW OF NORTH AMERICA, INC.

R-12 and R-134a systems use different leak detectors. An R-12 leak detector will not detect R-134a leaks (R-134a molecules are much smaller than R-12 molecules). However, an R-134a leak detector will detect R-12 leaks (be sure to follow the manufacturer's instructions carefully to avoid contamination).

An R-12 leak detector uses a very sensitive pickup which indicates the presence of Freon when placed below the leak: a white light illuminates or a warning buzzer sounds. It is easier to find a leak with the engine off, provided the pressure in the A/C system is 70-80 psi overall (slightly overcharged).

Always check for leaks with the engine off. The radiator fan of a running engine will circulate the refrigerant around making the leak point difficult to locate.

To check the evaporator, put the leak detector in the drain of the housing or in the center dash vent.

An R-134a leak detector has been tested and approved by BMW, TIF 5550. It automatically calibrates after it is turned on, and it detects leaks as small as 0.40 oz. of R-12 or R-134a per year.

BMW does not recommend the use of dyed refrigerant for finding a leak. The dyes can sometimes impair system operation and may damage the interior fabrics of the car.