How it Works: Pressure Switches
Air-conditioning systems use pressure switches to regulate the pressure from with inside the system. They are there to prevent component failure. There are many different types of pressure switches, here is a sample of a few.
Low Pressure Cut Out Switch (LPCO)
The LPCO is used to shut off the compressor if the air conditioning system drops below a certain pressure, indicating there is not enough refrigerant. It works by cre-ating an open circuit to the electrical power supply to the compressor and saves it from being damaged. The switch is wired in series to the circuitry.
High Pressure Cut Out Switch (HPCO)
The HPCO is used to protect the system from excess pressure. It senses if the pressure in the system is too high it will create an open circuit to the electrical power supply to the compressor saving it from being damaged. The switch is wired in series to the circuitry.
High Pressure Relief Valve (Pop off valve)
These were quite common in early vehicles. They are located in the receiver drier, compressors and hoses and look like a raised round dot, they are designed to release refrigerant to the atmosphere if the pressure in the system gets too high, they work via a series of internal springs, once the pressure in the system returns to normal the springs close.
Compressor Cycling Switch
The Compressor cycling switch is used to control the compressor clutch and senses the pressure on the low side of the system, switching the compressor on when needed.
Fan Switch
This operates in the medium pressure range and is used to turn on and off the condenser fan while the Air Conditioning is operating.
Thermo Limiting Switch
The superheat switch has a fuse that will melt at a certain pressure. It works by creating an open circuit to the electrical power supply to the compressor and saves it from being damaged.
Pressure Transducer
This switch is usually located between the compressor and expansion valve, usually found on the discharge line. Its job is to tell the ECU the pressure the system is running at, by converting the pressure it senses into electrical voltage, this intern allows the ECU to either engage or disengage the clutch or turn on or off the vehicles cooling fans and also increase engine idle when Air Conditioning system is in operation.
Binary Switch
This switch has two different circuits, it does the job of a high and low pressure switch, creating an open circuit at each end of the pressure scale, to the electrical power supply to the compressor and saving it from being damaged (lack of lubrication). The switch is wired in series to the circuitry.
Trinary Switch
This switch has three different circuits to it , The first two are the high and low pressure switch, creating an open circuit ,at each end of the pressure scale, to the electrical power supply to the compressor and saving it from being damaged (lack of lubrication). The third is a pressure switch to turn the condenser fan on and off during Air Conditioning operation.
Low Pressure Cut Out Switch (LPCO)
The LPCO is used to shut off the compressor if the air conditioning system drops below a certain pressure, indicating there is not enough refrigerant. It works by cre-ating an open circuit to the electrical power supply to the compressor and saves it from being damaged. The switch is wired in series to the circuitry.
High Pressure Cut Out Switch (HPCO)
The HPCO is used to protect the system from excess pressure. It senses if the pressure in the system is too high it will create an open circuit to the electrical power supply to the compressor saving it from being damaged. The switch is wired in series to the circuitry.
High Pressure Relief Valve (Pop off valve)
These were quite common in early vehicles. They are located in the receiver drier, compressors and hoses and look like a raised round dot, they are designed to release refrigerant to the atmosphere if the pressure in the system gets too high, they work via a series of internal springs, once the pressure in the system returns to normal the springs close.
Compressor Cycling Switch
The Compressor cycling switch is used to control the compressor clutch and senses the pressure on the low side of the system, switching the compressor on when needed.
Fan Switch
This operates in the medium pressure range and is used to turn on and off the condenser fan while the Air Conditioning is operating.
Thermo Limiting Switch
The superheat switch has a fuse that will melt at a certain pressure. It works by creating an open circuit to the electrical power supply to the compressor and saves it from being damaged.
Pressure Transducer
This switch is usually located between the compressor and expansion valve, usually found on the discharge line. Its job is to tell the ECU the pressure the system is running at, by converting the pressure it senses into electrical voltage, this intern allows the ECU to either engage or disengage the clutch or turn on or off the vehicles cooling fans and also increase engine idle when Air Conditioning system is in operation.
Binary Switch
This switch has two different circuits, it does the job of a high and low pressure switch, creating an open circuit at each end of the pressure scale, to the electrical power supply to the compressor and saving it from being damaged (lack of lubrication). The switch is wired in series to the circuitry.
Trinary Switch
This switch has three different circuits to it , The first two are the high and low pressure switch, creating an open circuit ,at each end of the pressure scale, to the electrical power supply to the compressor and saving it from being damaged (lack of lubrication). The third is a pressure switch to turn the condenser fan on and off during Air Conditioning operation.
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