General Description

The heating system is an air side controlled unit, i.e. the temperature is regulated by the mixing ratio of cold and warm air with help of the temperature mixing flap.

All outlets can be heated. Flaps are operated via cables. The water flow rate through the heater is regulated by an electromagnetic water valve in the water return circuit. It is switched ON and OFF by the temperature control via a track circuit with loop contact. The valve will be closed where the temperature control is set to less than 20°C (68°F). The valve is open without electric power.

With air conditioning the refrigerant is injected via an expansion valve, which is located in the housing on the right side.
A mechanical thermostat switch, located on left side of the unit, is used for protection against freezing.

With air conditioning the fresh air/bypass air can be operated for extremely fast cooling of the passenger compartment or elimination of disturbing odors.
The flaps are located in front of both blowers and are operated by two positioning motors.

Air conditioning equipment includes an additional, 2-speed, electric fan. This fan always runs at least in 1st speed when the air conditioner is switched ON.
Regardless of air conditioner operation 1st speed of extra fan is switched ON as from a coolant temperature of 89 - 93°C (192 - 199°F) and switched OFF with a coolant temperature of 86 - 82°C (187 - 180°F).
Regardless of air conditioner operation 2nd speed of extra fan is switched ON as from a coolant temperature of 97 - 101°C (207 - 214°F) and switched OFF with a coolant temperature of 94 - 90°C (201 - 194°F).

The drier has one high pressure and one low pressure safety switch. The high pressure switch stops the compressor when reaching a refrigerant pressure of 25.5 - 17.7 bar (363 - 252 psi) and switches the compressor ON again when refrigerant pressure drops to 22.5 - 20 bar (320 - 284 psi). The low pressure switch stops the compressor when refrigerant pressure drops to 2.22 - 1.72 bar (32 - 24 psi) and switches the compressor ON again when refrigerant pressure rises to 2.0 - 2.4 bar (28 - 34 psi).
These safety switches help prevent damage to the air conditioning system.