Evacuation

CAUTION: R-134a systems require use of special service equipment designed specifically for R-134a systems. R-12 servicing equipment cannot be used on R-134a systems. Vacuum pumps suitable for removing air and moisture from A/C systems are commercially available. A specification for system pump down used here is 28-29 1/2 inches vacuum. This reading can be attained at or near sea level only. For each 1000 feet of altitude, reading will be one inch of vacuum less than standard specification given. For example, at 5000 feet elevation, only 23-24 1/2 inches of vacuum can be obtained. System must be completely discharged before it can be evacuated. Damage to vacuum pump will result if pressurized refrigerant is allowed to enter pump assembly.

1. Connect vacuum pump to gauge manifold. With gauges connected into system, remove cap from vacuum hose connector. Install center hose from gauge manifold to vacuum pump connector. Open high and low side gauge manifold hand valves.
2. Operate vacuum pump a minimum of 30 minutes for air and moisture removal. Watch compound gauge to see that system pumps down into a vacuum. System will reach 28-29 1/2 inches vacuum in a maximum of five minutes. If system does not pump down, check all connections and leak test if necessary.
3. Close gauge manifold hand valves and shutoff vacuum pump.
4. Check ability of system to hold vacuum. Watch compound gauge to see that gauge does not rise at a faster rate than one inch vacuum every four or five minutes. If compound gauge rises at too rapid a rate, install partial charge and leak test.
5. If system holds vacuum, charge system with refrigerant.