Air Conditioning Control System; Refrigeration Temperature Control; Security Protection Control - Lifan 620 Maintenance Manual

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When engine works, heated by the high temperature of the engine cylinder, the coolant is pumped
into the heat exchanger through water pipe by the water pump of the cooling system. Air from
blower can take the heat given off by the coolant into the vehicle or the windscreen to raise the
temperature in the vehicle or defrost. After the cooling process in the heat exchanger, coolant is
pumped back by water pump. Repeating the circulation can make warm air heating. See Figure
6-4:
Figure 6-4
III. Air conditioning control system
Air conditioning system includes power control circuit, compressor clutch control circuit and safety
protection control circuit and data communication circuit. It mainly consists of air conditioning
switch, air conditioning controller (electrical air conditioning system), coolant temperature sensor,
pressure switch, solenoid valve and temperature controller, etc. Air conditioning control system is
to guarantee the effective work of air conditioning system under any circumstances, and
guarantee the safe operation of the air conditioning system and the engine.

1. Refrigeration temperature control

It mainly consists of evaporator temperature sensor, A/C controller and relevant circuits, etc.
When the temperature of evaporator changes, the resistance of sensor changes accordingly,
making A/C controller receive the relevant voltage signal of the temperature. Amplified by the
amplifying circuit, the signal is to control the work of electromagnetic clutch relay: when connecting
electromagnetic clutch relay, compressor electromagnetic clutch connects, compressor starts to
work, and the temperature will decrease; when disconnecting the electromagnetic clutch relay,
compressor electromagnetic clutch disconnects, compressor stops working, and the temperature
will increase. By controlling compressor, air conditioning control system maintains the refrigeration
temperature in the set range.
2. To reduce the engine load under certain circumstances, electronic fuel injection engine also
controls the compressor: when engine starts, drives off, suddenly accelerates and overspeeds, the
air conditioner compressor stops working.

3. Security protection control

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