The gaseous refrigerant is sucked in by the compressor and then compressed. As a result of this compression, the refrigerant heats up to a temperature between 70 degrees Celsius and 110 degrees Celsius.
The gas is then pumped to the condenser. The condenser has numerous cooling fins through which the gas is pumped. The gaseous refrigerant is then cooled by the passing flow of fresh air or, depending on the model, by the auxiliary fan until it condenses.
The condensed, i.e. liquid refrigerant is then passed through a fixed orifice tube. Downstream of the fixed orifice tube the pressure and therefore the temperature of the refrigerant drop rapidly.
The fixed orifice tube is mounted upstream of the entrance to the evaporator, in which the refrigerant then evaporates. This cools the evaporator and at the same the passing air flow.
The cooled air passes through the air distribution system of the heater/air conditioning system to reach the inside of the vehicle.
The gaseous refrigerant is then passed through the collector/dehydrator before it is drawn into the compressor again and the cooling system cycle repeats itself.
In the condenser, the heated, pressurized, gaseous refrigerant condenses to form a liquid under high pressure. As this occurs, the stored heat is given up to the passing air by the condenser.
Accumulator/dehydrator
NOTE:If any of the main components such as the compressor, condenser, evaporator or refrigerant lines is exchanged then the dehydrator/accumulator must always be renewed. The collector/dehydrator must also be renewed if the system has been open for longer than two hours.
Any moisture present in the refrigerant is extracted in the collector/dehydrator. The collector/dehydrator also ensures that the refrigerant evaporates completely. It thus protects the compressor from "liquid hammer".
If the pressure and the temperature drop together in the evaporator, and the temperature approaches freezing point, there is a danger that the evaporator will ice up, and therefore lose its cooling ability. The low pressure switch will then switch off the compressor at 1.5 Bar, and when the pressure has risen suitably, switches it back on at 2.9 Bar.
Introduction - Freshline
Available since 04/1998 as a cooling van.
The condenser in the refrigeration system is identical with that of the usual air conditioning system. A special evaporator and a modified compressor are used. The system pressure is controlled using an expansion valve. The all-round insulation of the refrigerated compartment is made of a material with a particularly high heat insulation value. The inner cladding is made of coated high-impact plastic (ABS) and is safe for use with foodstuffs.
CAUTION:The polyurethane hard foam insulation is highly flammable. Before any welding work is carried out rear of the passenger compartment, the hard foam insulation must be removed over a wide area.
No air conditioning is available for the passenger compartment if the vehicle has a refrigeration system. The evaporator installed in production remains in the vehicle after conversion, but must not be connected.
The refrigeration system is the same as that used in the Transit refrigerated van. There is additional de-icing equipment fitted, which prevents icing up of the evaporator and resultant loss of cooling ability. This is done by a "de-icing line", which takes hot, gaseous refrigerant from the line between the compressor and condenser and feeds it into the evaporator. This de-icing procedure can either be performed manually by pressing a button on the operating panel, or set to occur automatically once an hour.
NOTE:The tube must not be obstructed.
The water which condenses is passed through a tube to the outside.
General
During the winter months the air conditioning should be switched on for approx. 10 minutes to ensure that the sealing of the system remains intact. To do this, set the temperature control switch to "Warm" and the A/C switch to recirculated air to turn on the air conditioning.
Refrigerant losses of approx. 100 g/year can occur. The condition of the refrigerant lines and clamps should be checked, particularly for signs of chafing. The system should generally be refilled after approximately two years.
To prevent the evaporator from icing up, the air conditioning does not work at temperatures below 3°C.
If during a leakage inspection of the air conditioning a leak is detected on a compressor shaft seal, then this seal should not be renewed immediately. However, if the seal is still leaking after running the air conditioning for 15 minutes then a new one should be installed.
Procedure when water enters the footwell from the air conditioning system
Please check the following points and repair affected vehicles accordingly.
- Make sure that the air conditioning run-off line is connected to the heater.
- Make sure that the air conditioning run-off line is correct.
- Make sure that the run-off line is not kinked.
- Remove the plastic bush at the end of the line and clean the run-off line.
