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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017
Note
♦ The cause of this fault could also be too much refrigerant oil
in the circuit. Overfilling with refrigerant oil can occur if the re‐
frigerant oil level was not checked after the air conditioner
compressor was renewed.
♦ Further notes regarding this ⇒ page 241 .
Possible deviation from specification during pressure test
•
•
High pressure and low pressure normal
The requisite cooling output in the evaporator of the heating and air conditioning unit and in the evaporator
lk
for cooling the high-voltage components is not reached.
or
•
High pressure and low pressure normal
•
•
The air conditioner compressor is noisy (especially immediately after being switched on)
The requisite cooling output in the evaporator of the heating and air conditioning unit (and/or in the evap‐
orator used to cool the high-voltage components) is not reached.
Possible causes for deviation from specification and rectification
♦ One of the pressure/temperature senders or temperature sensors on or in the refrigerant circuit supplies
incorrect values ⇒ Vehicle diagnostic tester in “Guided Fault Finding” mode and ⇒ Heating, air conditioning;
Rep. gr. 87 ; Overview of fitting locations - air conditioning system
♦ Actuation and function of air conditioner compressor faulty ⇒ Vehicle diagnostic tester in “Guided Fault
Finding” mode.
♦ One of the valves installed in the refrigerant circuit is defective or is not working properly ⇒ Heating, air
conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-specific workshop manual).
♦ Too much refrigerant in circuit.
♦ Expansion valve for the evaporator in the front heating and air conditioning unit defective.
♦ Too much refrigerant oil in circuit.
– Check the measured values of the various pressure/temperature senders and temperature sensors during
operation of the air conditioning system, renew components with false measured values ⇒ Vehicle diag‐
nostic tester in “Guided Fault Finding” mode and ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of
fitting locations - air conditioning system .
– Check the actuation and function of the air conditioner compressor and repair ⇒ Vehicle diagnostic tester
in “Guided Fault Finding” mode
– Check the function and actuation of the various valves and pressure/temperature senders installed in the
refrigerant circuit by means of the pressure distribution in the refrigerant circuit ⇒ Vehicle diagnostic tester
in “Guided Fault Finding” mode and ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant circuit (vehicle-
specific workshop manual).
– If no fault can be found, extract the refrigerant from the refrigerant circuit.
•
The quantity of refrigerant extracted is significantly greater than the prescribed charge quantity:
– Recharge the refrigerant circuit and repeat the test.
The quantity of refrigerant extracted is about equal to the prescribed charge quantity:
•
– Clean the refrigerant circuit (flush with R1234yf refrigerant ⇒ “1.6 Cleaning refrigerant circuit”, page 92 ).
– Pour in the correct amount of refrigerant oil in the circuit (see note).
Final measures
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Rep. gr.87 - Air conditioning system
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