Roof-top air-conditioning system CC4E
Webasto Thermosysteme
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6.8.
Post-repair procedures and testing
Check refrigerant pressures and pressure switches function tests
a)
General
Every air-conditioning system filled with refrigerant is in a state of overpressure, which is equal
throughout the system circuit and which depends on ambient temperature.
During operation of the system, the working pressure on the intake side differs from that on the
delivery side of the compressor. The pressures differ and are influenced by the compressor
operating speed, the temperature inside the vehicle, the outside air temperature and relative
humidity. Abnormal working pressures indicate that there is a fault in the system.
The working pressure should be tested with an on-board power supply of 24-26 V and at air
temperatures between 20 °C and max. 40 °C. The fan must be operated at full power stage 3. The
hood must be fitted for the pressure test and to test the pressure monitors, since the air pressure of
the heat exchangers has a decisive influence on whether or not the operating pressure is reached.
The following values must be obtained:
If different pressure values are obtained, an authorized repair shop must be consulted to investigate
the reasons.
When the pressure test is complete, disconnect the pressure gauges and refit the sealing caps.
b)
Testing the high-pressure monitor
– Connect pressure gauges to system.
– Remove fuse F3 (condenser fan) and fit the hood.
– Switch on the air-conditioning system.
– Check whether compressor switches off at a pressure of 26.5 ± 2 bar.
– Remove the hood and refit fuse F3 (condenser fan).
– Check that compressor switches on again when pressure drops to 20 ± 2 bar.
c)
Perform complementary steps.
IMPORTANT
If the high pressure switch is not working properly, switch off the air-
conditioning system immediately, as refrigerant will be discharged via the
pressure relief valve as soon as the pressure reaches 34.5 bar.
Replenishing partially filled systems with refrigerant
a)
General notes
Normally there is no consumption of refrigerant. A loss of refrigerant may only occur due to leaks
after some time of operation.
The performance of the air-conditioning system will be reduced if the refrigerant level drops below
the minimum level. Extreme loss of refrigerant results in deactivation of the low pressure switch.
Outside air
temperature
Low pressure gauge
High pressure gauge
27 °C
4.0 bar abs ± 0.2 bar
10 bar abs ± 2 bar
30 °C
4.2 bar abs ± 0.2 bar
11 bar abs ± 2 bar
35 °C
4.5 bar abs ± 0.2 bar
13 bar abs ± 2 bar
40 °C
4.9 bar abs ± 0.2 bar
15 bar abs ± 2 bar
