Purging the Test Hoses

Purging the Test Hoses

1. With the manifold test set attached to the system.
2. Purge the high pressure test hose by cracking open the high pressure side hand valve on the manifold gauge set for 3 to 5 seconds. This allows the system refrigerant to purge the air from the test hose and discharge through the manifold centre test hose. Immediately close the high pressure side hand valve.
3. Purge the low pressure test hose in the same manner by cracking open the low pressure side hand valve manifold gauge set for 3 to 5 seconds, then close the hand valve.

Stabilising the System

The manifold gauge set is now attached to the system and the test hoses purged of air. With both hand valves closed, the system must be operated for a few minutes to stabilise all pressures and temperatures throughout the system in order to obtain accurate test gauge readings.

Proceed as follows:

1. Place all test hoses, gauge set and other equipment away from all engine moving parts. Also keep the hoses from touching the hot engine manifold.
2. Start the engine and adjust engine speed to fast idle
3. Turn on the air conditioning and set for maximum cooling with blower fans on high speed
4. Open the car doors and/or windows (to quickly eliminate car interior heat).
5. Operate the system under these conditions for 5 to 10 minutes to stabilise the system ready for testing.
6. Check the system for full refrigerant by noting the sight glass indications. Some refrigerant loss occurs over a period of time.

Note: The air conditioning system must contain a full refrigerant charge before an accurate system check can be made. An insufficient charge is indicated by a stream of bubbles or foam. If the refrigerant charge is low, the system must be fully discharged into a refrigerant recovery station and recharged with the correct weight of refrigerant 82.30.08. Do not top up a system with refrigerant.

Leak Test

A high proportion of all air conditioning work consists of locating and repairing leaks.

Many leaks are located at connections and are caused by vibration. They may only require the re-tightening of a connection or clamp.

Occasionally a hose rubs on a structural part of the vehicle and creates a leak, or a hose deteriorates which will require a replacement.

The specified maximum leakage rate at each fitting is 0.5 kg of R 134a in 40 years and a leak detector capable of operating to this accuracy must be provided. To check place the leak detector probe at the lowest point of each joint, pause for two seconds. Do not wave the probe about as refrigerant is heavier than air and flows to the lowest point. If a leak is greater than 0-5 kg in forty years is detected identify the leak point for rectification.

Check that the leaking fitting has been tightened to the correct torque. If the torque is low, rectify and repeat leak test. If the torque is satisfactory, depressurise the system, dismantle the leaking connection and check the quality of the fitting.

If the fitting is satisfactory, clean and reassemble after applying a thin film of refrigerant to the seat of a flare fitting, or a new oiled “O” ring to an “O” ring fitting.

Tighten to the correct torque.

Charge the system with 200 g of E134A and leak test the rectified system. If the system is satisfactory, depressurise, evacuate and recharge the system.

If the system is unsatisfactory, i.e. leakage greater than 0.5 kg in forty years, depressurise and replace the leaking assembly.