High pressure cut-off switch. High pressure relief valve
DESCRIPTION The high pressure cut-off switch is located on the
discharge line near the compressor. The switch is
screwed onto a 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. OPERATION The high pressure cut-off switch is connected in
series electrically with the electronic cycling clutch
switch, the low pressure cut-off switch, and the Heater-
A/C controls 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 will open
when the discharge line pressure rises above about
3100 to 3375 kPa (450 to 490 psi). The switch contacts
will close when the discharge line pressure
drops to about 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. DESCRIPTION A high pressure relief valve is located on the compressor
cylinder head, which is at the rear of the
compressor. This mechanical valve is designed to
vent refrigerant from the system to protect against
damage to the compressor and other system components,
caused by condenser air flow restriction or an
overcharge of refrigerant. OPERATION The high pressure relief valve vents the system
when a discharge pressure of 3445 to 4135 kPa (500
to 600 psi) or above is reached. The valve closes with
a minimum discharge pressure of 2756 kPa (400 psi)
is reached.
The high pressure relief valve vents only enough
refrigerant to reduce the system pressure, and then
re-seats itself. The majority of the refrigerant is conserved
in the system. If the valve vents refrigerant, it
does not mean the valve is faulty.
The high pressure relief valve is a factory-calibrated
unit. The valve cannot be adjusted or
repaired, and must not be removed or otherwise dis-turbed. The valve is only
serviced as a part of the
compressor assembly.High pressure cut-off switch
High pressure relief valve
Dodge Durango (DN) 1998-2003 Service Manual
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