Nissan Pathfinder: Heater & Air Conditioning System - Component Parts

Component Parts Location

Heating and Cooling Unit Assembly

This system utilizes a heating and cooling unit that combines the heating unit and cooling unit into an assembly.

Heater Core

Hot coolant from the engine is passed through a winding tube of the core. Fins attached to the core tubes serve to increase surface for heat transfer to air that is forced past them, by a fan, thereby heating the passenger compartment.

Expansion Valve

Refrigerant temperature is detected by the temperature sensing part, located in the low-pressure refrigerant path inside the expansion valve. The lift amount of the high-pressure side ball valve is changed to regulate the refrigerant flow.

1.	Sensing part	2.	Shaft	3.	Ball valve
4.	Diaphragm
A.	From evaporator (low-pressure side)	B.	To evaporator (high-pressure side)	C.	From liquid tank
D.	To electric compressor
	Refrigerant flow

Evaporator

• A thin laminate pipeless evaporator is used.

• The mist from liquid refrigerant transforms to gas by evaporation by the air conveyed from front blower motor. The air is cooled by the heat by evaporation.

  

  1.	Inlet	2.	Outlet	3.	Refrigerant flow
  	Front

Compressor

Intakes, compresses, and discharges refrigerant to circulate refrigerant inside the refrigerant cycle.

Condenser

The sub-cool section further cools the liquid refrigerant, increasing the amount of heat that the liquid refrigerant can absorb and improving cooling performance.

1.	Liquid tank	2.	Sub cool part (over cool part)	3.	Inlet
4.	Outlet
	Gas refrigerant		Gas and liquid		Liquid

Liquid Tank

• A liquid tank compatible with R-1234yf refrigerant is used.

• Eliminates foreign matter in refrigerant and temporarily stores liquid refrigerant.

1.	Outlet	2.	Inlet	3.	Sub cool part (over cool part)
4.	Liquid tank
	Gas refrigerant		Gas and liquid		Liquid

High-Pressure and Low-Pressure Pipe

Transfers heat out of the liquid refrigerant, sub cooling it below condensation temperature.

Refrigerant Cycle

Refrigerant System Protection

REFRIGERANT CYCLE

Refrigerant Flow

The refrigerant from the compressor flows through the condenser and liquid tank, evaporator, and returns to the compressor. The refrigerant evaporation in the evaporator is controlled by an expansion valve.

Freeze Protection

To prevent evaporator from freezing up, the evaporator air temperature is monitored and the voltage signal to the A/C auto amp. makes the A/C relay go OFF and stop the compressor.

REFRIGERANT SYSTEM PROTECTION

Refrigerant Pressure Sensor

• The refrigerant system is protected against excessively high or low pressures by the refrigerant pressure sensor, located on the liquid tank. The refrigerant pressure sensor detects the pressure inside the refrigerant line and sends the voltage signal to the ECM if the system pressure rises above or falls below the specifications.

• ECM turns the A/C relay to OFF and stops the compressor when the high-pressure side detected by refrigerant pressure sensor to have the following conditions:

  • Approximately 3,120 kPa (31.8 kg/cm², 452 psi) or more (Engine speed is 1,500 rpm or more.)

  • Approximately 2,740 kPa (27.9 kg/cm², 397 psi) or more (Engine speed is less than 1,500 rpm.)

  • Approximately 120 kPa (1.2 kg/cm², 17 psi) or less

Pressure Relief Valve

The refrigerant system is also protected by a pressure relief valve, located in the rear head of the compressor. The release port on the pressure relief valve automatically opens and releases refrigerant into the atmosphere when the pressure of refrigerant in the system increases to an unusual level [more than 3,800 kPa (38.8 kg/cm², 551 psi)].

Precautions ++Interior