Specifications

A/C System Components

3-13

TOYOTA Air Conditioning and Climate Control – Course 752

o reduce the overall length of the engine, accessories may be driven by

just one or two belts. The A/C compressor and power steering pump are

usually driven by the same belt. However, if the compressor were to seize,

the belt could break which would cause a loss of power steering assist.

A belt protection system is used on all Toyota models to reduce the

potential safety hazard of a loss of power steering.

The belt protection circuit of the A/C amplifier or ECU monitors the

following signals:

• Engine rpm

(Ne) is monitored at the Engine Control Module (ECM) or

at the ignitor.

• Compressor shaft rpm is measured by a magnetic pickup in the side of

the compressor housing.

The amplifier or A/C ECU will compare these signals to determine if Ne is

different from the compressor rpm by

more than 60 percent for more

than 0.6 seconds.

If it does, the system will:

• De-energize the compressor clutch relay. This will disengage the

compressor clutch.

• The amplifier will also cause the indicator lamp in the A/C button or

display to flash (to alert the driver of the malfunction).

•

The system will reset when the ignition is switched OFF then ON again.

Belt Protection

Sensor

Belt Protection

Sensor

• Signals ECU that

compressor is locking.

• See text below.

Lock Sensor

Pulse Plate

Fig. 3-15

752f315

Front Shaft

Magnet

O-Ring

Coil

Exit

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