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Air conditioning systems with refrigerant R1234yf - General information - Edition 07.2017
♦ No cooling or insufficient cooling from one or two evaporators
(on vehicles with 2nd heater and air conditioner/evaporators).
*
♦ Actuation of the air conditioner compressor (via the air condi‐
tioning system magnetic clutch - N25- or the air conditioner
compressor regulating valve - N280- ) is switched off by the
respective control unit (e.g. the operating and display unit for
front air conditioning system - E87- , the air conditioning sys‐
tem control unit - J301- or the Climatronic control unit - J255- )
due to pressure in the refrigerant circuit being too high or too
low * ⇒ Vehicle diagnostic tester in “Guided Fault Finding”
mode - air conditioning system.
♦ The electrical air conditioner compressor - V470- is not actu‐
ated by the control unit for air conditioning compressor - J842-
due to pressure being too high or too low * ⇒ Vehicle diagnostic
tester in “Guided Fault Finding” mode - air conditioning system
and battery regulation.
♦ If fresh air supply is lacking or drops significantly after a few
miles (evaporator iced up) *⇒ Vehicle diagnostic tester in “Gui‐
ded Fault Finding” mode - air conditioning system.
In addition, the following problems may occur:
lk
The air conditioner compressor is noisy.
– Re-tighten the securing bolts for the air conditioner compres‐
sor and the air conditioner compressor bracket using a torque
wrench ⇒ Heating, air conditioning; Rep. gr. 87 ; Refrigerant
circuit; System overview - refrigerant circuit .
– Check the routing of the refrigerant lines. These must not rest
against other components and must not be under any strain
(realign them if necessary) ⇒ Heating, air conditioning; Rep.
gr. 87 ; Refrigerant circuit; System overview - refrigerant cir‐
cuit .
Noises (refrigerant hammering) occur immediately after the air
conditioning is switched on and/or in a curve or when the brakes
are applied:
– Drain the refrigerant circuit, evacuate it and recharge (too
much refrigerant or refrigerant oil in the circuit) ⇒ page 129
and ⇒ “2.14 Checking pressures”, page 170 .
Note
Excess refrigerant oil in the circuit may also cause this problem
(e.g. if the refrigerant oil level was not checked after the air con‐
ditioner compressor was renewed) ⇒ page 79 .
Water sprays out of the vents (in dash panel or footwell) although
air conditioning system is otherwise functioning properly:
– Check condensation drain to ensure that it is routed correctly.
It should not be kinked or crushed ⇒ Heating, air conditioning;
Rep. gr. 87 ; Front heater and air conditioner .
– The condensed water drain valve must not be hindered in its
operation by wax or underbody sealant and must open and
close properly ⇒ Heating, air conditioning; Rep. gr. 87 ; Front
heater and air conditioner .
– Check plenum chamber cover. It must not be damaged and
must be installed correctly (no water should run into the evap‐
orator) ⇒ Heating, air conditioning; Rep. gr. 87 ; Overview of
fitting locations - air conditioning system; Overview of fitting
locations - components outside passenger compartment .
1. Refrigerant circuit
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