Toyota 4Runner manuals

Toyota 4Runner: System Description

SYSTEM DESCRIPTION

1. GENERAL

(a) The air conditioning system has the following controls.

Control

Outline

Manual Control

The air conditioning amplifier assembly controls the damper positions (air inlet control damper, air mix control damper and mode control damper) and blower speed in accordance with the positions of the switches (temperature control dial, blower dial, mode operation switch and REC/FRS switch).

Air Inlet Control

Drives the recirculation damper servo sub-assembly according to the operation of the REC/FRS switch and moves the dampers to the fresh or recirculation position.

Compressor Control

The air conditioning amplifier assembly compares the A/C pulley speed signals, which are transmitted by the ECM (crankshaft position sensor). When the air conditioning amplifier assembly determines that the A/C pulley is locked, it turns off the magnet clutch assembly.

Defroster Control

Defroster control logic is used to improve defroster performance.

Defroster Fresh Air Mode Switching Control

Defroster fresh air mode switching control changes the system from recirculation air mode to fresh air mode to improve defroster performance.

MAX Air Conditioning Control

When the temperature control dial is in the MAX A/C position, the air conditioning amplifier assembly turns the air conditioning compressor on and activates the recirculation damper servo sub-assembly to set the air inlet control damper to the recirculation position*, thereby improving cooling efficiency.

Rear Defogger Control

When the ignition switch is ON and the rear defogger switch is pushed, the system is activated to keep the defogger heater on for approx. 15 minutes. However, the operating time of the rear defogger can be extended up to approx. 255 minutes when both of the following requirements are met:

  • Ambient Temperature: 0°C (32°F) or less
  • Vehicle Speed: 50 km/h (31.1 mph) or more

Diagnosis

A Diagnostic Trouble Code (DTC) is stored in memory when the air conditioning amplifier assembly detects a problem with the air conditioning system.

  • *: w/o DEF, FOOT/DEF mode

2. MODE POSITION AND DAMPER OPERATION

Function of Main Damper





Control Damper

Operation Position

Damper Position

Operation

Air Inlet Control Damper

Fresh

A

Brings in fresh air.

Recirculation

B

Recirculates internal air.

Air Mix Control Damper

MAX COOL to MAX HOT

E - D - C

Varies the mixture of cold air and hot air in order to regulate the temperature continuously from hot to cool.

MAX COOL Damper

MAX COOL

V

Open in the MAX COOL position.

Except MAX COOL

W

Close in all position except MAX COOL position.

MAX HOT Damper

MAX HOT

Y

Open in the MAX HOT position.

Except MAX HOT

X

Closed in all position except MAX HOT position.

Mode Control Damper

Face

F, I, N, T, X

Air blows out of the front center registers, side registers and rear face registers.

Bi-level

G, L, N, T, X

Air blows out of the front center registers, side registers, rear face registers and front and rear footwell register ducts.

Foot

H, M, P, T, W, Y (MAX HOT position)

H, M, O, T, X (Except MAX HOT position)

Air blows out of the front and rear footwell register ducts.

In addition, air blows out slightly from the front defroster, side registers, front center registers and rear face registers.

Foot/Def

H, K, R, T, W, Y (MAX HOT position)

H, M, Q, T, X (Except MAX HOT position)

Defrosts the windshield through the front defroster and side registers while air is also blown out from the front and rear footwell register ducts.

In addition, air blows out slightly from the front center registers and rear face registers.

Def

H, I, S, U, X

Defrosts the windshield through the front defrosters.

3. AIR OUTLETS AND AIRFLOW VOLUME




























Indication

(Mode)

Front Center Register

Side Register

Front Footwell Register

Rear Face Register

Rear Footwell Register

Front Defroster

A

B

C

D

E

F

Face

-

-

-

Bi-level

-

Foot

Foot/Def

Def

-

-

-

-

-

HINT:

The size of the circle indicates the proportion of airflow volume.

4. A/C LOCK SENSOR

The A/C lock sensor sends A/C pulley speed signals to the air conditioning amplifier assembly. The air conditioning amplifier assembly determines whether the A/C compressor is locked or not by using those signals and engine speed signals.

5. NO. 1 COOLER THERMISTOR

The No. 1 cooler thermistor detects the temperature of the cool air immediately after it passes through the evaporator in the form of resistance changes, and outputs the temperature to the air conditioning amplifier assembly.

6. BLOWER WITH FAN MOTOR SUB-ASSEMBLY

The blower with fan motor sub-assembly has a built-in blower controller, and is controlled by the air conditioning amplifier assembly using duty control.

7. AIR CONDITIONING HARNESS ASSEMBLY (BUS CONNECTOR)

(a) A BUS connector is used in the wire harness that connects the servo motor to the air conditioning amplifier assembly.


Connector Type

Connected to

*1: Bus connector

Damper servo sub-assembly LH (mode damper servo)

*2: Bus connector

Damper servo sub-assembly RH (air mix damper servo)

*3: Bus connector

Recirculation damper servo sub-assembly

*4: Bus connector

Air conditioning amplifier assembly

*5: Connector

No. 1 cooler thermistor

(b) Each BUS connector has a built-in communication/driver IC which communicates with each servo motor connector, actuates the servo motor, and has a position detection function.


8. SERVO MOTOR

(a) The pulse pattern type servo motor detects the relative position using 2-bit on/off signals.

The forward and reverse revolutions of this motor are detected using two signals, A and B, which output four types of patterns. The air conditioning amplifier assembly counts the number of pulse patterns in order to determine the stopped position.


9. QUICK HEATER ASSEMBLY (w/ PTC Heater)

(a) General

(1) The PTC heater is located above the heater core in the air conditioner unit.

(2) The PTC heater consists of a PTC element, aluminum fins and brass plates. When current is applied to the PTC element, it generates heat to warm the air that passes through the unit.


(b) PTC Heater Operating Conditions

(1) The on/off operation of the PTC heater is controlled by the air conditioning amplifier assembly in accordance with the engine coolant temperature, ambient temperature, engine speed, air mix setting and electrical load (generator power ratio).

For example, the number of operating PTC heaters varies according to engine coolant temperature as shown in the graph below.


10. COOLER THERMISTOR (AMBIENT TEMPERATURE SENSOR)

The cooler thermistor (ambient temperature sensor) detects the outside temperature based on changes in the resistance of its built-in thermistor and sends a signal to the air conditioning amplifier assembly.

Precaution
PRECAUTION 1. IF ANY OF FOLLOWING CONDITIONS ARE MET, KEEP ENGINE IDLING (ENGINE SPEED AT LESS THAN 2000 RPM) WITH AIR CONDITIONING SWITCH ON FOR AT LEAST 2 MINUTES Refrigerant gas has been ...

System Diagram
SYSTEM DIAGRAM Communication Table Transmitter Receiver Signal Communication Line Air conditioning amplifier assembly ECM ...

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