Automotive Air Conditioning Theory, ..............Procedures.......................And Diagnosis.

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BASIC R12 TO R134a Conversion 



RECOVER ANY R12 IN THE SYSTEM Remove all R12 refrigerant using approved recovery equipment.  When complete, the system must hold a vacuum for 5 minutes.  if the system shows a positive pressure after 5 minutes, repeat the recovery process.
REMOVE THE R12 MINERAL OIL* It is recommended that R12 mineral oil be removed from the system being retrofitted.  This can be accomplished by draining individual components or by approved flushing systems.
REPLACE THE ACCUMULATOR OR RECEIVER-DRIER Remove the used accumulator or receiver-drier and install a new replacement unit that contains desiccant designed for R134a systems. 
PERFORM SYSTEM REPAIRS Make necessary system repairs.  check the condition of expansion valve, orifice tube and pressure switches.  If bad, replace now,  Check engine cooling system performance (Radiator, fan and shroud).
INSTALL AN IN-LINE FILTER If the compressor is replaced, installation of an in-line filter on accumulator type systems is required to protect the compressor .
HIGH PRESSURE CUT-OFF SWITCH Installation of a high pressure cut-off switch may be necessary on some vehicles to insure compressor durability.
INSTALL R-134a SERVICE PORT FITTINGS Installation of R134a service port fittings is required by law.   DETAILS
APPLY R134a LABEL Complete  retrofit label  and affix in a prominent position in the engine compartment.  This is required by law.
ADD R134a LUBRICANT Add the correct amount of A/C lubricant for the particular system that is being retrofitted.
EVACUATE THE SYSTEM* Evacuate the system for 45 to 60 minutes.
CHARGE WITH R134a* Determine the correct charge for the system being upgraded to R134a use.  In most cases, the R134a charge will be 10% less than the R12 charge.
PERFORM LEAK TEST Leak test the system using equipment that will detect R134a refrigerant.
ROAD TEST THE VEHICLE A 3-5 degree Fahrenheit increase in duct outlet temperature is not unusual.  Adjusting the clutch cycling switch to reduce the cutoff pressure by 2 pounds (maximum recommended adjustment) or the installation of an auxiliary condenser fan may be necessary to reduce the duct temperature on some vehicles.




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