CAUTIONARY POINTS FOR MAINTENANCE
G-5spec tableR-12 vs R-134a system part and tool incompatibilities documented.
(Cont'd)
Refrigerant systems comparison (continued)
Joint nuts
R-12 systemInch threads
R-134a systemMetric threads
RemarksThread standards for joint nuts connecting cooler pipes and hoses have been changed to avoid connecting R-12 system parts with R-134a system parts.
Joint blocks
R-12 systemRefer to remarks
R-134a systemRefer to remarks
RemarksThe bolt sizes and part measurements for joint blocks connecting cooler pipes and cooler hoses have been changed to avoid connecting R-12 system parts with R-134a system parts.
Charging valve
R-12 systemScrew-on type Hi: 3/8-24 UNF Lo: 7/16-20 UNF
R-134a systemQuick-connect type Hi: 16 mm {0.6 in} dia. Lo: 13 mm {0.5 in} dia.
RemarksThe shape of the charging valve differs for each system to avoid confusion. The quick-connect charging valve prevents refrigerant from leaking when the charging hose is connected to the valve.
Service tools
Service tools comparison
Tool joints
R-12 systemInch threads
R-134a systemMetric threads
RemarksThread standards for tool joints have been changed to avoid connecting R-12 system tools with R-134a system tools.
Charging valve joints
R-12 systemScrew-on type Hi: 3/8-24 UNF Lo: 7/16-20 UNF
R-134a systemQuick-connect type Hi: 16 mm {0.6 in} dia. Lo: 13 mm {0.5 in} dia.
RemarksThe shape of the charging valve joints differs for each system to avoid confusion. The quick-connect charging valve joint prevents refrigerant from leaking when the charging hose is connected to the valve.
Manifold gauge
R-12 systemHigh-pressure-side maximum reading: 2.9 MPa {30 kgf/cm2, 430 psi}
R-134a systemHigh-pressure-side maximum reading: 3.5 MPa {35 kgf/cm2, 500 psi}
RemarksR-134a requires a higher pressure to condense than R-12.
Leak tester
R-12 systemGas type Electric type
R-134a systemElectric type
RemarksA gas leak tester reacts with chlorine in R-12 to indicate the location of a leak. This kind of tester does not work with an R-134a system, however, because R-134a has no chlorine. Two kinds of electric testers are available: those that work exclusively with one system or the other and those that work with both.