Lotus Service Notes Section PL
Page 3
PL.1 - GENERAL DESCRIPTION
Heater System
The heater system uses engine coolant to provide a heat source transferred to the interior airstream via
a heat exchanger matrix mounted in an 'air blend' unit housed within the chassis well, ahead of the cabin
footwell. The coolant is fed from an outlet on the left hand side of the cylinder head, and via an alloy pipe
running along the outside of the RH chassis side rail to the matrix. Coolant is returned via a similar pipe along
the outside of the LH chassis rail to a by-pass return pipe on the left hand side of the engine.
Air temperature is controlled by a pair of air blend flaps within the heater housing which direct a varying
proportion of the airflow through, or around the matrix as determined by the position of the temperature selec-
tor knob. Note that no water valve is fitted, such that the matrix is always 'hot' when the engine is running.
Air Conditioning (If fitted) - Basic Principles
The air conditioning unit uses a cycling clutch system with a thermostatic expansion valve to provide
refrigerated air to the vehicle interior. The system comprises:
- a closed circuit containing refrigerant R134a;
- a compressor mounted on the front side of the engine, driven by multi-vee belt from the front end of the
crankshaft via an electromagnetic clutch;
- a condenser mounted horizontally at the front of the car, beneath the engine cooling radiator;
- an evaporator unit (cooler) fitted in the chassis well ahead of the cabin footwell;
- a thermostatic expansion valve fitted at the inlet connection to the evaporator;
- a receiver-drier unit mounted above the heater/a.c. unit
Closed Circuit
The closed refrigerant circuit should not be opened unless absolutely necessary, and only then using
appropriate refrigerant recovery equipment. Never allow the refrigerant to vent to atmosphere. Refer to sub-
section PL.5. Failure to observe these precautions may result in personal injury.
Expansion Trinary switch
valve
Service ports Condenser
Compressor
connections
Receiver-drier
High pressure
relief valve
Sill pipes
p75c
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