General Preparations, Discharging, Evacuating

General Preparations

Always conduct a visual inspection of the air conditioning system to identify any damage, excessive wear, refrigerant leaks (oil residue), improper belt adjust- ment, improper pulley alignment, and plugged condenser cooling fins.

Note: Never use water to clean the condenser or radiator fins. Using compressed air is the approved method.

Observe the refrigerant flow through the receiver/dryer sight glass (if equipped), use the correct gauges to check all systems, verify all system compo- nents and controls are operable, check for loose fittings, replace defective, worn, or damaged drive belts, and repair system leaks.

Note: The use of the sight glass alone to determine system charge level can be misleading. Normally operating and correctly charged variable displacement compressors and R-134a systems will have bubbles showing in the sight glass under certain conditions.

Discharging

Caution: Refrigerant R-12 has been identified as a compound which causes damage to the ozone layer. It is unlawful to discharge R-12 into the atmosphere. Subaru of America encourages you to handle R-12 in a responsible and safe manner, and according to Federal EPA guidelines and any local and state regulations. Always follow approved recovery/recycling procedures and utilize approved recovery/recycling equipment.

Discharging and recovery of the system refrigerant is required before replacement of major components of the system. It is also required when the system has a leak, or for the replacement of refrigerant oil. Discharging and recovery of the system refrigerant is the first step in preparing for major servicing, repair,

or replacement of components; the second step is evacuation.

Evacuating

Evacuating the system removes air and moisture from the system. Discharge and recover the system refrigerant first; then follow the steps listed below to evacuate the system:

•Fully close both valves of the manifold gauge set.

•Connect a vacuum pump to the center charging hose of the manifold gauge set.

•Start the vacuum pump.

•Open the low- and high pressure valves slowly.

•When the pressure reading has reached approximately 29.00 in Hg, fully close both valves.

•Stop the vacuum pump.

•Wait 10 minutes, the pressure reading should not change. If it changes, there is a leak in the system.

Note: Certain types of system leaks such as loose fittings may not be discovered using this method. Always recheck the system with a leak detector after the system is charged.

	Evacuating The System

Elevation		Vacuum of System
m (ft)		mm Hg, in Hg
0 (0)	710		27.95

300 (1,000)	685		26.97

600 (2,000)	660		25.98

900 (3,000)	635		25.00

Note: Values show readings of the low-pressure gauge.

Elevation/Pressure Relationship

R-12, R-134A specifications

Subaru, a renowned automotive manufacturer, has made significant advancements in its air conditioning refrigerant technologies, particularly in its use of R-12 and R-134A. Understanding these refrigerants is crucial for enthusiasts and technicians alike, as they are integral to Subaru's climate control systems.

R-12, also known as dichlorodifluoromethane, was commonly used in automotive air conditioning systems until the late 20th century. It is a chlorofluorocarbon (CFC) that proved to be highly efficient in cooling systems, offering optimal performance in various conditions. However, environmental concerns over ozone depletion led to a phasedown of its use. Subaru vehicles produced before the early 1990s often utilized R-12, characterized by its stable properties and excellent thermodynamic performance. Despite its effectiveness, the negative environmental impact of R-12 has rendered it obsolete in modern automotive applications.

Adapting to these challenges, Subaru transitioned to R-134A, or tetrafluoroethane, in the 1990s. R-134A is a hydrofluorocarbon (HFC) that does not deplete the ozone layer, making it a more environmentally friendly alternative to R-12. This transition coincided with Subaru's commitment to sustainability and compliance with international regulations. R-134A boasts several advantages, including lower global warming potential and improved efficiency in cooling performance. Its thermodynamic properties provide effective heat absorption, ensuring that Subaru drivers can rely on consistent climate control, regardless of external temperatures.

Subaru has integrated R-134A into its vehicle technology without compromising performance. Newer models utilize advanced HVAC systems that maximize refrigerant efficiency while maintaining comfort. Features such as variable compressor speed control enhance overall system performance, allowing for quicker cooling response and reduced energy consumption. Additionally, Subaru employs meticulous system designs to minimize refrigerant leakage, further supporting environmental initiatives.

The transition from R-12 to R-134A exemplifies Subaru's responsiveness to both performance and environmental concerns. As regulations continue to evolve, it's expected that Subaru will continue to innovate in refrigerant technology, prioritizing sustainability while delivering reliable and efficient climate control for its drivers. As vehicle technology advances, it's clear that Subaru remains committed to adapting its systems for a cleaner, more efficient future.