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11.2 A/C loop lubrication
Oil circulates throughout the whole A/C loop:
g
Compressor
g
Condenser
g
Expansion valve or orifice tube
g
Evaporator
g
Receiver drier or Accumulator
The oils used in air conditioning fulfill the following
functions:
g
Lubricating the compressor
g
Cooling the compressor
g
Improving the sealing of the compression parts
g
Expelling impurities from the loop by circulation
g
Improving the sealing of the joints in the loop
The two main families for the automotive air
conditioning market are:
g
Synthetic Polyalkylene glycol oils (PAG)
g
Synthetic Polyolester oils (POE), used for electric
compressors in hybrid vehicles.
11.2.1 Oils and compressor technologies
Mechanically driven compressors
g
3 types of synthetic oil
g
All Polyalkylene glycol (PAG)
g
ISO46 - ISO100 - ISO125
Electrically driven compressors
g
1 type of synthetic oil
g
Polyolester (POE)
11.2.2 Oil and refrigerant types
The traditional oil for R134a applications cannot be
used for the new HFO1234YF refrigerant.
A new generation of PAG oil has been developed to
be compatible for both uses.
Oils are hygroscopic (readily absorbing moisture
from the air).
The mix of humidity, refrigerant and oil produces
acid matter in the air conditioning loop.
Over time, these acids corrode the circuit.
Therefore it is essential to extract these acids and
other residues in regular maintenance operations
and to renew the refrigerant and the oil.
Similarly, bottles of fresh oil, and any other contai-
ners, must not be left open or they will absorb
humidity themselves.
11.2.3 Oils in the catalogue
The volume and viscosity of the oils to be used are
shown in the table of vehicle products.
11. The components
of the A/C Loop
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