Searching For Refrigerant Circuit Leaks With Compressed Air Or Nitrogen

NOTE:

A leak can be identified if a maximum of pressure of 15 bar (217.55 psi) can be generated in the refrigerant circuit using clean, dry compressed air or nitrogen. Refer to REFRIGERANT CIRCUIT, CLEANING WITH COMPRESSED AIR AND NITROGEN . If the leak is large enough, the sound of escaping air or gas can be heard at the location of the leak.

Use the service connection for the compressed air or nitrogen.

Fig 1: Identifying Quick-Release Coupling Adapter For Service Connections

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

The quick-release coupling adapter for service connections can be connected to the air compressor using a modified filler hose -A- (for example, with 5/8" 18 UNF threads, different from the threads on the quick-release coupling adapter) and a suitable adapter -B-. To prevent moisture, oil or contaminants from the air compressor from entering the A/C system refrigerant circuit, also use a combination fine-gauge filter for compressed air systems such as those that are standard in paint shops. Install it between the compressed air system and the filler hose -A-. Refer to Special Tools and Equipment Catalog.

Fig 2: Charging Hose With Connection To Workshop Compressed-Air System

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

A compressed gas cylinder filled with nitrogen -3- can be connected to the closed refrigerant circuit using a pressure gauge battery with a pressure reducer for nitrogen (maximum reduction pressure: 15 bar (217.55 psi)) -1- and a filler hose -2- (for example, with 5/8" 18 UNF threads) connected to the service connection (a quick-release coupling adapter has to be connected to the service connections).

Fig 3: Identifying Pressure Gauge Set With Pressure Reducer For Nitrogen (Maximum Reducing Pressure: 15 Bar)

Courtesy of VOLKSWAGEN GROUP OF AMERICA, INC.

-- Slowly increase the pressure in the refrigerant circuit to a maximum of 15 bar (217.55 psi).

-- Find the location of the leak by listening for the sound of venting gas. An Ultrasonic Tester VAG1842S :VAG1842S  will aid in detecting the origin of noise.

-- Use clean, dry compressed air to force the nitrogen out of the refrigerant circuit. The nitrogen must not get into the Service bottle. Reason: gases that do not condense do not get into the Service bottle.

-- Repair the leak.

-- Evacuate and again observe the vacuum display over a period of hours. Only when the vacuum is maintained can the refrigerant circuit be charged.

• If there is a leak that is small enough that no air or very little air vents through it and the A/C Service Station can generate a sufficient vacuum. The vacuum indicator does not increase after switching off the A/C Service Station or only increases slowly, indicating that air is only entering through a small leak.

-- Add 100 grams of refrigerant to the circuit, find the location of the leak using an electronic leak detector and repair it or add UV contrast dye to the refrigerant and find the location of the leak with the Leak Detection Kit :VAS6201  or succeeding model and repair it. Refer to REFRIGERANT CIRCUIT, TRACING LEAKS, WITH Electronic Leak Detector  or REFRIGERANT CIRCUIT, TRACING LEAKS, WITH Leak Detection System .

-- Empty the refrigerant circuit, if necessary. Refer to REFRIGERANT CIRCUIT, DISCHARGING WITH A/C Service Station .

-- Evacuate and check the vacuum display again over several hours. Only when the vacuum is maintained can the refrigerant circuit be charged.