Toyota 4Runner: System Description

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:

Diagnosis

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

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.

Face

-

-

-

Bi-level

-

Foot

Foot/Def

Def

-

-

-

-

-

*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