Specifications

Section 3

The electromagnet allows A/C operation to be controlled by an electric

ircuit. The compressor clutch relay is also controlled by a temperature

signal from the evaporator and a pressure switch in the refrigerant line.

In most systems, the compressor clutch cycles ON and OFF periodically to

allow the evaporator to warm up (defrost) during periods of high cooling

demand. An evaporator cold enough to freeze moisture around it does not

transfer heat as well.

Some variable capacity compressors don’t use a magnetic clutch. Instead

they use a

Damper Limiter (DL)-type drive pulley. This pulley uses a

damper to absorb torque fluctuations of the engine and a limiter

mechanism. In case the compressor locks, the limiter mechanism causes

the spoke portion of the pulley to break. This separates the pulley from

the compressor shaft and prevents the drive belt from breaking. To

reduce pulley weight, the pulley portion is made of plastic.

3-12

TOYOTA Technical Training

Damper

Limiter Pulley

• Absorbs tor

que

fluctuations.

• Protects drive belt if

compr

essor locks.

Spoke Portion

Damper

Limiter Mechanism

Fig. 3-14

752f314

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