The air conditioning (A/C) system contains a fixed orifice tube and is controlled by the low-pressure cut-off switch. R134a refrigerant is used.
6
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Evaporator core orifice
8
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High-pressure (liquid and warm)
9
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Low-pressure (liquid and cool)
10
-
Low-pressure (gaseous and cool)
11
-
High-pressure (gaseous and hot)
The A/C compressor (2) is driven by the engine. The compressor primes the gaseous refrigerant out of the suction accumulator (3) and compresses it. The refrigerant heats up and is passed to the condenser (1) under high pressure.
At this point heat is drawn from the refrigerant by the air being forced past the cooling fins. Because of this heat loss, the refrigerant liquifies and leaves the condenser.
A fixed orifice tube (6), which separates the refrigerant at high pressure from that at low pressure, is located between the condenser and the evaporator (5). This fixed orifice tube slows down the flow of the refrigerant from the compressor, so that pressure builds up in the condenser.
After passing through the fixed orifice tube the liquid refrigerant expands in the circuit to the evaporator. In the evaporator the liquid refrigerant converts back into the gaseous state and this causes heat to be extracted from the air coming into the vehicle. The air therefore cools down and the moisture it contained is given up at the evaporator. The refrigerant stream coming from the evaporator enters the suction accumulator and is primed up again by the compressor.
The system is protected by the high-pressure cut-off switch, in order to prevent damage by excessive pressure (example, because of overfilling). If the pressure exceeds the maximum allowed, the high-pressure cut-off switch turns off the compressor.
The working cycles of the A/C compressor are controlled by the low-pressure cut-off switch depending on the low pressure in the suction accumulator. The low-pressure cut-off switch turns the A/C compressor off permanently if the pressure falls below the approved value (example, if there is a leak).
