I. Function of Compressor Cutout

General
Should the refrigerant compressor block the electromagnetic clutch is switched off via a control unit to protect the single belt drive.


Design of compressor cutout:
1. Speed sensors
2. Control unit
3. Microswitch (only in vehicles with diesel engine and automatic transmission)







L1 Speed sensor, refrigerant compressor







L3 Speed sensor,starter ring gear (at ring gear of flywheel in diesel engine)


1. Speed sensors
The speed sensors measure the speeds of the engine and refrigerant compressor. They consist of a magnetic core and a coil. If the ring gear or the Shaft of the refrigerant compressor is rotating, an alternating voltage is induced in the coils of the speed sensors, and this is passed on to the control unit (N6).

The alternating voltage and frequency rise and fall according to the rotational speeds.


NOTE: In vehicles with gasoline engine, the engine speed is registered by terminal TD at the terminal block of the diagnosis plug.







N6 Compressor cutout control unit


2. Compressor cutout control unit (N6)
The control unit compares the two speeds from the engine and refrigerant compressor sensors and switches off the refrigerant compressor if the speeds differ by approx. 30%.







S27/1 Microswitch







3. Microswitch (S27/1), only In model 201.1 with automatic transmission
The microswitch switches off the refrigerant compressor via the control unit (N6) at full throttle at engine speeds under approx. 1050 rpm up to approx. 2150 rpm (to improve moving off).


Function description of compressor cutout
In vehicles up to 01/88, the refrigerant compressor is only switched on approx. 10 seconds after an engine speed of approx. 600 rpm is reached (to stabilize the engine speed). In vehicles as of 02/88, the refrigerant compressor is switched on after 4 seconds in model 201.0 or immediately in model 201.1.

The control unit (N6) only compares the two speeds of the ring gear and the refrigerant compressor 2 seconds after the refrigerant compressor cuts in (due to slip in the clutch when switching on). If there is a difference in speed of more than 30% when the refrigerant compressor cuts in, this condition is monitored for 200 milliseconds. If the speed difference no longer exists after 200 milliseconds, the refrigerant compressor remains switched on. If the speed difference remains due to sluggishness in the refrigerant compressor, the control unit (N6) switches off the refrigerant compressor immediately.

This procedure is only repeated after the ignition has been switched off and the engine started again.


Emergency cutout of refrigerant compressor







S25/3 110 °C temperature switch Engine 102 RUF/CAT except models 201.034/035 RUF/CAT







S25/5 105/115 °C temperature switch in models 201.034/035 RUF/CAT







S25/5 105/115 °C temperature switch, engine 602


In order to prevent thermal overload of the engines, the refrigerant compressor is switched off as follows:

a) In vehicles with engine 102 RUF/CAT and engine 602, it is switched off by a temperature switch (S25/3 or S25/5) via the compressor cutout control unit. At a coolant temperature of 110 or 115 °C, the temperature switch switches to ground causing the compressor cutout control unit to switch off the refrigerant compressor.

When the engine temperature drops to 103 or 108 °C, the temperature switch opens and the refrigerant compressor is switched back on again immediately by the compressor cutout control unit.