From the FSM:
LOW PRESSURE CYCLING
CLUTCH SWITCH
The low pressure cycling clutch switch is located
on the top of the accumulator. The switch is screwed
onto an accumulator fitting that contains a Schrader type
valve, which allows the switch to be serviced
without discharging the refrigerant system. The
accumulator fitting is equipped with an O-ring to
seal the switch connection.
The low pressure cycling
clutch switch is connected
in series electrically with the high pressure cut-off
switch, between ground and the Powertrain Control
Module (PCM). The switch contacts open and close
causing the PCM to turn the compressor clutch on
and off. This regulates the refrigerant system pressure
and controls evaporator temperature. Controlling
the evaporator temperature prevents condensate
water on the evaporator fins from freezing and
obstructing air conditioning system air flow.
The low pressure cycling
clutch switch contacts are
open when the suction pressure is approximately 141
kPa (20.5 psi) or lower. The switch contacts will close
when the suction pressure rises to approximately 234
to 262 kPa (34 to 38 psi) or above. Lower ambient
temperatures, below approximately -1° C (30° F), will
also cause the switch contacts to open. This is due to
the pressure/temperature relationship of the refrigerant
in the system.
The low pressure cycling
clutch switch is a factory calibrated
unit. It cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.
HIGH PRESSURE CUT-OFF SWITCH
The high pressure cut-off switch is located on the
discharge line near the compressor. The switch is
screwed onto a discharge line fitting that contains a
Schrader-type valve, which allows the switch to be
serviced without discharging the refrigerant system.
The discharge line fitting is equipped with an O-ring
to seal the
switch connection.
The high pressure cut-off switch is connected in
series electrically with the low pressure cycling
clutch switch between ground and the Powertrain
Control Module (PCM). The switch contacts open and
close causing the PCM to turn the compressor clutch
on and off. This prevents compressor operation when
the discharge line pressure approaches high levels.
The high pressure cut-off switch contacts are open
when the discharge line pressure rises above 3100 to
3375 kPa (450 to 490 psi). The switch contacts will
close when the discharge line pressure drops to 1860
to 2275 kPa (270 to 330 psi).
The high pressure cut-off switch is a factory-calibrated
unit. The switch cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.