General System Procedures

System Evacuation

Once the system has been opened for repairs, it must be fully evacuated with a vacuum pump to remove all traces of moisture. Moisture may collect and freeze in the expansion valve which will block the refrigerant flow and prevent the cooling action. Moisture will also react with R12 and cause corrosion. Evacuate system as follows:
1. Remove protective cap from low pressure connection on the A/C system.
2. Check and oil the O-ring in the low pressure hose from the manifold of the charging station and connect it to the low pressure side of A/C system.
3. Remove protective cap from high pressure side of A/C system. Check and oil O-ring in high pressure hose from manifold of charging station and connect it to the high pressure side of A/C system.
4. Ensure inlet valve and vent valve of charge cylinder (charging station) are closed. If charge cylinder contains refrigerant, close the outlet valve.
5. Fully open low pressure valve, high pressure valve and vacuum valve. Switch vacuum pump on and note low pressure gauge to ensure a vacuum is being created in the system by the vacuum pump.
6. Continue to operate until a vacuum of 17.5 mb is obtained. If vacuum cannot be obtained as specified, check system for leaks.
7. Run vacuum pump for a minimum of six minutes to ensure complete evacuation.
8. Close both gauge hand valves, switch off vacuum pump and observe low pressure side gauge reading.
9. Gauge reading should remain stationary at the point where the pump was switched off.
10. If gauge returns towards zero, a leak exists in the A/C system.
11. If gauge remains stationary for 3-5 minutes, close both manifold hand valves and disconnect hose from vacuum pump.