COMPRESSOR CLUTCH CONTROL
Evaporator Temperature Switch Although compressor clutch does not normally cycle on and off, an evaporator temperature switch turns off the compressor clutch if evaporator temperature decreases to 32øF (0øC). This prevents evaporator icing.
A/C Pressure Switch A/C pressure switch is a triple-pressure switch, which monitors high side pressure. See Fig. 1. If pressure decreases to less than 17.4 psi (1.2 kg/cmý), A/C pressure switch interrupts power to compressor clutch (low-pressure cutout). Switch closes when pressure increases to more than 34.8 psi (2.4 kg/cmý).
If pressure increases to more than 464 psi (32.6 kg/cmý), A/C pressure switch interrupts power to compressor clutch (highpressure cutout). Switch closes when pressure decreases to less than 348 psi (24.5 kg/cmý).
A/C pressure switch also controls cooling fan high speed operation. If pressure increases to more than 232 psi (16.3 kg/cmý), switch contacts close, causing cooling fan to operate at high speed. When pressure decreases to less than 181 psi (12.7 kg/cmý), switch contacts open.
Ambient Temperature Switch If ambient temperature decreases to less than 36øF (2øC), ambient temperature switch interrupts power to compressor clutch. When ambient temperature increases to more than 45øF (7øC), ambient temperature switch restores power to compressor clutch.
