Dodge Sprinter. Manual — part 339
A / C LOW PRESSURE SWITCH
DESCRIPTION
The rear A/C low pressure switch provides a signal
to the rear A/C control module to regulate the rear
refrigerant system pressure and control rear A/C
evaporator temperature (Fig. 9). The rear A/C control
module will disengage the rear A/C clutch if the rear
refrigerant system suction line pressure falls below
30 kPa (4.4 psi).
The rear A/C low pressure switch is mounted on a
fitting located on the rear suction line near the left
side of the rear A/C evaporator housing.
The rear refrigerant system must be discharge
prior to removing the rear A/C low pressure switch.
OPERATION
The rear A/C low pressure switch is electrically
connected in series with the rear A/C high pressure
switch, between ground and the rear A/C control
module.
The rear A/C low pressure switch contact opens or
closes the path the ground, signaling the rear A/C
control module to turn the rear A/C clutch on and off.
This regulates the rear refrigerant system pressure
and controls rear A/C evaporator temperature. Con-
trolling the rear evaporator temperature prevents
condensate water on the evaporator fins from freez-
ing and obstructing rear A/C system air flow.
The rear A/C low pressure switch contacts are open
when the rear suction line pressure is approximately
152 kPa (22 psi) or lower. The rear A/C low pressure
switch contacts will close when the rear suction line
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 rear
A/C low pressure switch contacts to open due to the
pressure/temperature relationship of the refrigerant
in the system.
The rear A/C low pressure switch is factory-cali-
brated and cannot be adjusted or repaired and, if
faulty or damaged, it must be replaced. Refer to the
appropriate wiring information for complete HVAC
wiring diagrams.
REMOVAL
WARNING: Refer to the applicable warnings and
cautions for this system before performing the fol-
lowing operation (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - WARNINGS) and (Refer
to 24 - HEATING & AIR CONDITIONING/PLUMBING -
CAUTIONS). Failure to follow the warnings and cau-
tions could result in possible personal injury or
death.
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the cover from the rear A/C evaporator
housing (Refer to 24 - HEATING & AIR CONDI-
TIONING/DISTRIBUTION - REAR/A/C EVAPORA-
TOR COVER-REAR - REMOVAL).
(3) Recover the refrigerant from the rear refriger-
ant system (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY).
(4) Remove the insulating tape from around the
area of the rear A/C low pressure switch (Fig. 10).
(5) Disconnect the wire harness connector from the
rear A/C low pressure switch.
(6) Remove the rear A/C low pressure switch and
install a plug into, or tape over the opened rear suc-
tion line fitting.
Fig. 9 Rear A/C Low Pressure Switch
1 - REAR PRESSURE SWITCH
2 - WIRE CONNECTOR
24 - 32
CONTROLS - REAR
VA
INSTALLATION
NOTE: Replacement of the PTFE thread sealing
tape is required anytime the rear A/C low pressure
switch is removed from the rear suction line line.
Failure to replace the sealing tape could result in a
rear refrigerant system leak.
(1) Remove the tape or plug from the rear suction
line fitting.
(2) Install PTFE thread sealing tape onto the rear
A/C low pressure switch and install the switch onto
the rear suction line. Tightened the A/C low pressure
switch to 10 N·m (88 in. lbs.).
(3) Connect the wiring harness connector to the
rear A/C low pressure switch.
(4) Install new insulating tape around the rear A/C
low pressure switch area.
(5) Reconnect the negative battery cable.
(6) Evacuate the rear refrigerant system (Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING
- STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE).
(7) Charge the rear refrigerant system (Refer to 24
- HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE).
(8) Install the cover onto the rear A/C evaporator
housing (Refer to 24 - HEATING & AIR CONDI-
TIONING/DISTRIBUTION - REAR/A/C EVAPORA-
TOR COVER-REAR - INSTALLATION).
BLOWER MOTOR RELAY
DESCRIPTION
The three rear blower motor relays used for the
rear A/C system are International Standards Organi-
zation (ISO)-type relays (Fig. 11). Relays conforming
to the ISO specifications have common physical
dimensions, current capacities, terminal functions
and patterns. The rear blower motor relays are elec-
tromechanical devices that switches fused battery
current directly to the rear blower motors. The rear
blower motor relays are energized when the relay
coils are provided battery current by the rear blower
motor switch (Refer to 24 - HEATING & AIR CON-
DITIONING/CONTROLS/BLOWER
MOTOR
SWITCH - DESCRIPTION).
The rear blower motor relays are located in the
relay block in the rear A/C evaporator housing.
OPERATION
The three ISO-standard rear blower motor relays
are electromechanical switches that uses a low cur-
rent input from the rear blower motor switch to con-
trol the high current output to the rear blower
motors. The movable, common feed relay contact is
held against the fixed, normally closed relay contact
by spring pressure. When the electromagnetic relay
coil is energized, it draws the movable common feed
relay contact away from the fixed, normally closed
relay contact and, holds it against the fixed, normally
open relay contact. This action allows high current to
flow to the rear blower motors.
When the relay coil is de-energized, spring pres-
sure returns the movable relay contact back against
the fixed, normally closed contact point. The resistor
Fig. 10 Rear A/C Low Pressure Switch
1 - INSULATING TAPE
2 - REAR A/C EVAPORATOR HOUSING
3 - WIRE HARNESS CONNECTOR
4 - REAR A/C LOW PRESSURE SWITCH
5 - REAR SUCTION LINE FITTING
Fig. 11 Rear Blower Motor Relays
1 - STANDARD ISO RELAY
2 - TERMINAL PATTERN
VA
CONTROLS - REAR
24 - 33
or diode is connected in parallel with the relay coil,
and helps to dissipate voltage spikes and electromag-
netic interference that can be generated as the elec-
tromagnetic field of the relay coil collapses.
The rear blower motor relay terminals are con-
nected to the vehicle electrical system through recep-
tacles in the relay block located in the rear A/C
evaporator housing.
The rear blower motor relays cannot be repaired
and, if faulty or damaged, they must be replaced.
Refer to the appropriate wiring information for diag-
nosis and testing of the ISO-standard relay and for
complete HVAC wiring diagrams.
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Remove the air filter from the rear A/C evapo-
rator housing (Refer to 24 - HEATING & AIR CON-
DITIONING/DISTRIBUTION - REAR/AIR FILTER -
REMOVAL).
(3) Reach up into the rear A/C evaporator housing
and remove the rear blower motor relays as neces-
sary from the relay block (Fig. 12).
24 - 34
CONTROLS - REAR
VA
INSTALLATION
(1) Position the rear blower motor relays into the
proper receptacle of the relay block located in the
rear A/C evaporator housing as necessary.
(2) Align the blower motor relay terminals with
the terminal cavities in the relay block receptacle
and push down firmly on the relay until the termi-
nals are fully seated.
(3) Install the rear air filter (Refer to 24 - HEAT-
ING
&
AIR
CONDITIONING/DISTRIBUTION
-
REAR/AIR FILTER - INSTALLATION).
(4) Reconnect the negative battery cable.
BLOWER MOTOR SWITCH
DESCRIPTION
The blower motor for the optional rear A/C system
is controlled by a three position rocker switch
mounted in the switch panel located on the instru-
ment panel (Fig. 13). The rear A/C blower motor
switch allows the selection of one of two blower
motor speeds and an Off position.
OPERATION
With the front A/C switch activated, the rear
blower motor speed can be selected by pressing the
rocker switch upwards (high speed) or downwards
(low speed). To turn the rear blower motor off, switch
the blower motor switch to the center position.
Depending on the blower motor switch position, a
blower motor speed command signal is sent to one of
the two blower motor relays. When activated, relay 1
sends power through an integral resistor within the
rear A/C control module and then to the blower
Fig. 12 Rear Blower Motor Relays
1 - REAR A/C EVAPORATOR HOUSING
2 - BLOWER MOTOR RELAY K204
3 - BLOWER MOTOR RELAY K203
4 - BLOWER MOTOR RELAY K201
5 - REAR CONDENSER FAN RELAY K205
6 - REAR COMPRESSOR RELAY K206
Fig. 13 Rear Air Conditioning Switch
VA
CONTROLS - REAR
24 - 35
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