General description and operation of the air conditioning system (Chevrolet Captiva 1)

Air conditioning system SP17

The SP17 is a 173cc fixed displacement swash plate compressor. It consists of five double ended pistons which move back and forth in 10 cylinders under the action of a swash plate and shaft assembly. There are 10 hemispherical support shoes connecting the pistons to the swash plate and shaft assembly. When the swash plate rotates, the shoes swing. In this way, the rotary motion of the swash plate is converted into reciprocating motion of the pistons.

System Components - Functioning

Compressor

All compressors are driven by a belt from the engine crankshaft through the compressor clutch pulley. The compressor pulley rotates without turning the compressor shaft until the electromagnetic clutch solenoid is energized. When the clutch solenoid is energized, the clutch driven disc and hub assembly is pulled back toward the pulley. The electromagnetic force of the clutch driven disc and pulley combines into one unit that turns the compressor shaft.

When the compressor shaft is driven to rotate, the low-pressure refrigerant vapor from the evaporator is compressed into high-pressure, high-temperature vapor. Compressor oil, used to lubricate the compressor, is carried along with the refrigerant. See "Major repair of the V5 air conditioning compressor" in this section.

Safety valve

The compressor is equipped with a relief valve installed in the system for safety purposes. Under certain conditions, the refrigerant pressure on the discharge side may exceed the rated operating value. To prevent damage to the system, the valve automatically opens at a pressure of approximately 3171 - 4137 kPa (460 - 600 psi) in the R-134a system. Conditions such as damaged pressure sensor, cooling fan failure, etc. that could cause the valve to open must be corrected. Refrigerant and compressor oil should be recharged if necessary.

Condenser heat exchanger

The condenser unit, located in front of the radiator, consists of a coil through which the coolant flows and cooling fins that ensure rapid heat transfer. Air passing through the condenser cools the high-pressure coolant vapor and causes it to condense into a liquid state.

Expansion valve

The expansion valve can fail in one of three positions: open, closed, or flow restriction.

An expansion valve that has failed in the open position will cause the air conditioning compressor to make noise or will not cool. This could be due to a broken spring, a broken ball, or excess moisture in the air conditioning system. If a defective spring or ball is found, the expansion valve should be replaced. If excess moisture is found in the air conditioning system, the refrigerant should be recharged.

An expansion valve stuck in the closed position will cause low suction pressure and no cooling. This may be due to a dome actuator failure or excessive moisture in the air conditioning system. If a defective expansion valve dome actuator is detected, the expansion valve must be replaced. If excessive moisture is detected in the air conditioning system, the refrigerant must be recharged.



Restriction of flow through the expansion valve causes low suction pressure and no cooling. This can be caused by a blockage in the refrigeration system. If blockage is suspected to be the cause of the problem, the refrigerant must be recharged, the expansion valve and receiver drier must be replaced.

Evaporator core

The evaporator is a device that cools and dries the air before it enters the car. High-pressure liquid refrigerant flows through an opening in the expansion tube and turns into low-pressure gas in the evaporator. The heat of the air passing through the evaporator heat exchanger is transferred to the cooling surface of the heat exchanger, which cools the air. As the heat is transferred from the air to the surface of the evaporator heat exchanger, moisture in the air condenses on the outer surface of the evaporator heat exchanger and is discharged outside as water.

Receiver-dryer

The sealed receiver-dryer unit is connected to the condenser outlet pipe. It serves as a refrigerant reservoir, receiving liquid and gaseous refrigerant, as well as compressor oil, into the evaporator.

At the bottom of the receiver-dryer there is a desiccant, which serves to remove moisture that may enter the system.

Heater core

The heater heat exchanger heats the air before it enters the vehicle. Engine coolant circulates in the heat exchanger to heat the outside air as it passes over the heat exchanger fins. The heat exchanger operates continuously and can be used to regulate the temperature of the conditioned air in the air conditioning mode, as well as in the heating and ventilation modes.

Control Panel

The air conditioning system is controlled by switches on the control panel. The heating and ventilation panel, mounted on the console, contains the following elements:

Three rotary control knobs

1. Temperature control knob

• The regulator controls the cable.
• Regulates the mixing of fresh outside air with heated air inside the vehicle to maintain an individually set temperature.
• To increase the temperature of the air entering the car, turn the handle to the right, into the red sector of the regulator.

2. Rotary mode switch knob

• It is driven by an electric motor.
• Controls the distribution of air between the windshield, instrument panel and floor vents.

3. Fan rotary control knob

• Turns on the electric fan at one of four speeds.
• In the OFF position, the fan turns off.
• It operates completely independently of the mode switch that controls the glass heating flap and the temperature control knob.
• Changes the fan speed in all modes and at any position of the temperature control. However, if the rotary fan control knob is in the off position, the air conditioning system is turned off regardless of the position of the air conditioner switch.

Three keys

1. Air conditioner key

• Controls the air conditioner.
• When you press the button, the air conditioner turns on and the indicator light comes on. For the air conditioner to work, the fan rotary control must be in one of the four speed positions.

2. Rear window heating button

• Controls the rear window heating.
• Turns on the rear window heating when the button is pressed and the indicator lamp lights up.

3. Ventilation key

• Switches the operating mode between recirculating the air in the cabin and supplying outside air into the cabin.
• In the initial position, ventilation works. The signal lamp lights when air recirculation in the passenger compartment is turned on.
• The intake ventilation flap is driven by an electric motor.

The electric fans of the engine cooling system operate continuously when the air conditioner is on. This additional function is part of the functions of the air conditioning control system and is designed to prevent excessive increase in compressor temperature. In addition, it allows for increased efficiency of the air conditioning system. The operation of the cooling fans is controlled by the electronic engine control system (ECM) via the cooling fan relay.

Pressure sensor

The pressure sensor functions as a high and low pressure cut-off relay together with a fan periodic switch. The pressure sensor is located on the high pressure liquid pipe, behind the right headlight, between the inside of the right front fender and the air filter. The signal from the pressure sensor goes to the ECM, which controls the compressor operation depending on the pressure signal.

Compressor cut-off at wide open throttle (WOT)

When accelerating at full throttle, the throttle position sensor (TPS) sends a signal to the ECM, which controls the compressor clutch.

The original source of the article is the website: ChevyMan.ru