Component Description

WARNING: This page is about a different car, the 2019 Nissan NV3500 HD, 2019 Nissan NV2500 HD, and 2019 Nissan NV1500. However, it is still accessible from the selected car via links, so may be relevant.

Component	Description
A/C Compressor	Vaporized refrigerant is drawn into the A/C compressor from the evaporator, where it is compressed to a high pressure, high temperature vapor. The hot, compressed vapor is then discharged to the condenser.
Ambient sensor	The ambient sensor measures the temperature of the air surrounding the vehicle. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
BCM	The BCM receives the fan ON and A/C ON signals from the front air control and sends a compressor ON request to the ECM.
ECM	The ECM sends a compressor ON request to the IPDM E/R based on the status of engine operation and load as well as refrigerant pressure information. If all the conditions are met for A/C operation, the ECM transmits the compressor ON request to the IPDM E/R. The ECM shares the refrigerant pressure sensor signal, engine RPM, and engine coolant temperature with the front air control via CAN communication line.
Fuse Block (J/B)	Located in the passenger compartment, behind the left lower IP, the Fuse Block (J/B) contains the front blower motor relay-1 and several fuses required for the air conditioner control system.
Front air control	The front air control controls the operation of the A/C and heating system based on inputs from the temperature control knob, the mode switches, the blower control dial, the ambient temperature sensor, the intake sensor, and inputs received from the ECM and combination meter across the CAN. Diagnosis of the front air control can be performed using the CONSULT. There is no self-diagnostic feature available.
Front air mix door motor	The air mix door controls the mix of hot or cold air that enters the ventilation system. It is controlled by the front air control based on the position of the temperature dial. The air mix door motor receives position commands from the front air control and reports actual door position back via an LCU (Local Control Unit) installed inside the motor. Commands and responses are sent across the LIN (Local Interconnect Network) to each motor simultaneously, with each motor having its own unique address, thereby only responding to requests sent to its specific address. The LCU reads the door position from a Position Balanced Resistor (PBR), also part of the motor, and returns that information to the front air control. The LCU switches the polarity of the circuits connected to the DC motor to drive the motor forward or backward as requested by the front air control. If the air mix door moves to a position less than 5% or more than 95% of its expected or allowed positions, the front air control will set a DTC.
Front blower motor	The front blower motor varies the speed at which the air flows through the ventilation system. The blower control dial has 26 detents allowing for 26 different fan speeds.
Front blower motor relay-1	The front blower motor relay-1 controls the flow of current to fuse 10 in the Fuse Block (J/B). The relay is connected directly to ground, and is energized when the ignition switch is in the ON or START position.
Front blower motor relay-2	The front blower motor relay-2 controls the flow of current to fuse 18 in the Fuse Block (J/B). The relay is connected directly to ground, and is energized when the ignition switch is in the ON or START position. This relay is necessary to provide additional current carrying capacity to the front blower motor.
Front mode door motor	The mode door controls the direction the conditioned air passes through the ventilation system. Through a series of levers and gears, the mode door controls the defrost door, the foot door, and the vent door. There are 5 preset positions: VENT, B/L, FOOT, D/F, and DEF. The FOOT position can be set to allow some airflow through to the defroster vent, or to completely block the defroster vent using the CONSULT. The mode door motor receives position commands from the front air control and reports actual door position back via an LCU (Local Control Unit) installed inside the motor. Commands and responses are sent across the LIN (Local Interconnect Network) to each motor simultaneously, with each motor having its own unique address, thereby only responding to requests sent to its specific address. The LCU reads the door position from a Position Balanced Resistor (PBR), also part of the motor, and returns that information to the front air control. The LCU switches the polarity of the circuits connected to the DC motor to drive the motor forward or backward as requested by the front air control. The mode door has 5 expected positions and, therefore, can set up to 5 DTCs if the expected position is not reported back to the front air control.
Heater pump (if equipped)	The heater pump improves heater performance specifically at idle conditions. It is designed to operate in either of the following 2 situations: Front blower motor set to maximum speed and temperature control dial set to full hot or Engine coolant temperature (signal via CAN communication) minus heater core outlet temperature (intake sensor input to front air control) is greater than 20 deg.C (68 deg.F). If the difference is less than 16 deg.C (61 deg.F), the heater pump will not operate unless the conditions in item No. 1 above are met.
Heater pump relay (if equipped)	The heater pump relay controls the flow of current to the heater pump. The relay is controlled by the front air control.
Intake door motor	The intake door motor controls the position of the intake door. Fresh air is allowed to enter the cabin in one position, and recirculated inside air is allowed to enter in the other position. At times the front air control may command partial fresh or recirculation based on evaporator or coolant temperatures. The intake door motor receives position commands from the front air control and reports actual door position back via an LCU (Local Control Unit) installed inside the motor. Commands and responses are sent across the LIN (Local Interconnect Network) to each motor simultaneously, with each motor having its own unique address, thereby only responding to requests sent to its specific address. The LCU reads the door position from a Position Balanced Resistor (PBR), also part of the motor, and returns that information to the front air control. The LCU switches the polarity of the circuits connected to the DC motor to drive the motor forward or backward as requested by the front air control. If the recirculation door moves to a position less than 5% or more than 95% of its expected or allowed positions, the front air control will set a DTC.
Intake sensor	The intake sensor measures the temperature of the front evaporator fins. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
IPDM E/R	Refer to System Diagram .
Power transistor	The power transistor controls the speed of the blower motor by controlling the ground circuit of the blower motor. The front air control provides voltage to the gate of the power transistor based on the position of the blower control dial. The power transistor is a metal-oxide semiconductor field effect transistor (MOSFET) that varies the ground side current of the front blower motor. By applying a variable voltage to the gate, the power transistor controls the current flow to ground, thereby controlling the speed of the blower motor.
Refrigerant pressure sensor	Refer to Component Function Check for VQ40DE and Component Function Check for VK56VD.
Water valve (if equipped)	The water valve cuts the flow of engine coolant to the front and rear heater cores to allow for maximum cooling during A/C operation. It is controlled by the front air control.