Heating and Air Conditioning: Description and Operation

REAR PASSENGER COMPARTMENT CLIMATE CONTROL
- A rear passenger compartment climate control system is standard equipment in model 140.057, and is available as a special order option in all other model 140 vehicles.
- The rear passenger compartment climate control system is a separate heating and cooling system which utilizes components familiar from the automatic climate control.
- The refrigerant circuit for rear passenger compartment cooling is connected in parallel with the existing air conditioning system.
- The refrigerant supply to the rear evaporator is controlled by a solenoid valve, located in the left front wheelhousing.
- For rear passenger compartment cooling, the (front) automatic climate control must be switched on.
- For rear passenger compartment heating, it is not necessary to switch on the (front) automatic climate control. The systems operate independent from one another.

Rear Passenger Compartment Control Panel:

- The left and right air outlet temperature can be separately adjusted via the left and right temperature wheels (1, 2).
- The rear passenger compartment climate control is switched on/off via the blower speed selector wheel (3). The system is switched on with the blower speed selector wheel (3) in any position except the "0" detent.
- The blower speed control is stepless and can be selected between 0 (detent, system OFF) and maximum speed.
- The electronic blower regulator (N29/2) is similar in function to the one installed in model 129.
- The rear passenger compartment climate control operates exclusively with recirculated air.

Rear Tunnel Flap Vacuum Valve (Y67/1) & Vacuum Elements (50 & 51):

- With the rear air conditioner switched on, the flaps for the rear footwell areas are closed by the (front) automatic climate control system. This changeover takes place via the rear tunnel flap vacuum valve (Y67/1) and vacuum elements (50 and 51).

Rear Passenger Compartment Control Panel:

- The slide regulator (6) controls the air distribution of the rear passenger compartment climate control between the rear center air outlets and rear footwell areas. The direction of air flow of the rear center air outlets is adjustable with the louvers (4) and (5).
- With all temperature selection wheels (front and rear) set to maximum red detent for maximum heat, the flaps for the rear footwell areas remain open.
- Using the two temperature selector wheels (1, 2), the heating or cooling capacity of the rear passenger compartment climate control can be controlled separately left and right, in accordance with the in-car temperature sensor (B1O/4).
- With the air conditioning system switched on, the system operates basically in a re-heat mode. This means that the intake air is first cooled by the evaporator and then heated by the heater core as needed.

Rear Heater Supply Unit (A31/1):

- The rear heater supply unit (A31/1) is located behind the side protection panel of the right front fender. The function and design (coolant circulation pump/left and right duovalves) corresponds to the supply unit of the front heating system.

Refrigerant Injection Valve (107) [arrow indicates direction of flow]:

- Instead of the familiar expansion valve refrigerant is injected into the rear evaporator by means of a refrigerant injection valve (107).

Refrigerant Shut-Off Valve (Y67):

- The refrigerant supply is controlled by a rear refrigerant shut-off valve (Y67).

Rear Fuse Box F4 (17-fuse, in trunk):

- The rear passenger compartment climate control is protected by the fuse box F4.