Electronic Leak Detectors

TESTING THE SYSTEM FOR LEAKS
Testing the refrigerant system for leaks is one of the most important phases of troubleshooting. One or more of the methods outlined will prove useful in detecting leaks or checking connections if service work is performed. Before beginning any leak test, attach a manifold gauge set and note pressure. If little or no pressure is indicated, a partial charge must be installed. Check all connections, compressor head gasket, oil filler plug and compressor shaft seal for leaks.

LEAK DETECTORS TYPES
There are a number of electronic leak detectors available to perform leak tests. Current versions of the electronic leak have three settings, one for R-12, one for R-134a and one for gross. The gross setting is for isolating very large leaks already found in one of the other two settings. Refer to operating instructions for the unit being used and observe these general procedures.

R134A / R12
R134a refrigerant is uniquely different from R12 refrigerant and requires some changes in the repair methods, tools and materials used in A/C service. Two important differences between R134a and R12 which affect the technicians ability to locate refrigerant leaks are:

1. The R134a molecule is smaller than the R12 molecule and therefore will leak through smaller openings. For the same size opening the smaller R134a molecule will leak out faster than the R12.

2. R134a refrigerant does not contain chlorine which the older R12 electronic leak detectors found very easy to identify. Many of today's electronic leak detectors have difficulty locating small R134a refrigerant leaks.


GENERAL TESTING PROCEDURES

CAUTION: Care should be taken to prevent personal injury which could occur due to touching a hot engine when testing. Tests should be done with the engine off and as cool as possible. Do not operate the detector in a combustible atmosphere since its sensor operates at a high temperature.

Prior to beginning the test, make sure that the refrigerant system is sufficiently charged for leak testing by measuring the static pressure with a gage set. System pressures above 345 kPa (50 psi) are acceptable to conduct a leak test.

The most common leaks are found at the refrigerant fittings or connections. This may be caused by improper torque, damaged seals (0-rings), lack of lubrication on the seals (0-rings), or dirt/debris across the seal (0-ring). Even the smallest piece of lint from cotton gloves or shop clothes can create a leak path across a seal (0-ring).

The successful use of the electronic leak detector depends greatly upon the scan rate and upon carefully following the manufacturer's instruction regarding calibration, operation, and maintenance.

Each joint must be completely circled, moving at 1 to 2 inches per second with the tip of the probe as close to the surface as possible but no more than 1/4 inch away and without blocking air intake. A leak is indicated when the audible tone goes from a steady 1 to 2 clicks per second to a solid alarm. The balance knob should be adjusted frequently to maintain the 1 to 2 clicks per second rate.

NOTE: Halogen leak detectors are sensitive to windshield washing solutions, many solvents and cleaners, and some adhesives used in the vehicle. Care should be taken to prevent a false warning by making sure surfaces are clean. Also, surfaces should be dry since ingestion of liquids will damage the detector. To ensure no gases are present that may cause a false warning, blow out engine compartment with air hose prior to test.


Be sure to check service access gauge port valve fittings, particularly when valve caps are missing, as dirt accumulations can destroy the sealing area of valve core when manifold gauge set is attached. Replace missing valve caps after cleaning valve core area. Valve caps should only be finger tightened. Using pliers to tighten valve caps may distort sealing surface of valve.

Check for leaks in manifold gauge set and hoses, as well as the rest of the system.


ADVICE FOR TROUBLE FREE OPERATION
DO NOT
- Press the probe up against a surface under test.
- Intentionally pull liquids into the probe.
- Block the air flow in the probe, the sensor momentarily overheats and will false alarm.
- Poke foam insulation with the probe. The foam contains refrigerant gas and the J 39400 will detect this as a leak.
DO
- Do keep plenty of spare filters on hand.
- Do change the filter often, daily if necessary.