Mercedes-Benz Sprinter / Dodge Sprinter. Service manual — part 506
OPERATION
The ISO-standard rear A/C clutch relay is an elec-
tromechanical switch that uses a low current input
from the rear A/C control module to control the high
current output to the rear A/C clutch. 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 con-
tact. This action allows high current to flow to the
A/C clutch field coil.
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
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 A/C clutch relay terminals are connected
to the vehicle electrical system through a receptacle
in the relay block located in the rear A/C evaporator
housing.
The rear A/C clutch relay cannot be repaired and,
if faulty or damaged, it must be replaced. Refer to
the appropriate wiring information for diagnosis 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 A/C clutch relay from the relay
block (Fig. 2).
Fig. 1 Rear A/C Clutch Relay
1 - STANDARD ISO RELAY
2 - TERMINAL PATTERN
VA
CONTROLS - REAR
24 - 25
INSTALLATION
(1) Position the rear A/C clutch relay into the
proper receptacle of the relay block located in the
rear A/C evaporator housing.
(2) Align the A/C clutch relay terminals with the
terminal cavities in the relay block receptacle and
push down firmly on the relay until the terminals
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.
A / C CONDENSER FAN RELAY
DESCRIPTION
The rear A/C condenser fan relay for the rear A/C
system is an International Standards Organization
(ISO)-type relay (Fig. 3). Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal functions and patterns.
The rear A/C condenser fan relay is an electrome-
chanical device that uses a low current input to con-
trol the high current output to the A/C condenser fan
for the rear heating-A/C system.
The rear A/C condenser fan relay is located in the
relay block in the rear A/C evaporator housing.
OPERATION
The ISO-standard rear A/C condenser fan relay is
an electromechanical switch that uses a low current
input from the rear A/C control module to control the
high current output to the rear A/C condenser cooling
fan. The movable, common feed relay contact is held
against the fixed, normally closed relay contact by
spring pressure. When the electromagnetic relay coil
Fig. 2 Rear A/C Clutch Relay
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. 3 Rear A/C Condenser Fan Relay
1 - STANDARD ISO RELAY
2 - TERMINAL PATTERN
24 - 26
CONTROLS - REAR
VA
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 electric cooling fan motor.
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
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 A/C condenser fan relay terminals are
connected to the vehicle electrical system through a
receptacle in the relay block located in the rear A/C
evaporator housing.
The rear A/C condenser fan relay cannot be
repaired and, if faulty or damaged, it must be
replaced. Refer to the appropriate wiring information
for diagnosis 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 A/C condenser fan relay from
the relay block (Fig. 4).
VA
CONTROLS - REAR
24 - 27
INSTALLATION
(1) Position the rear A/C condenser fan relay into
the proper receptacle of the relay block located in the
rear A/C evaporator housing.
(2) Align the A/C condenser fan relay terminals
with the terminal cavities in the relay block recepta-
cle and push down firmly on the relay until the ter-
minals 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.
A / C CONTROL MODULE
DESCRIPTION
The rear A/C control module (Fig. 5) is connected
to the rear A/C blower motor switch, rear evaporative
temperature sensor, rear A/C temperature control
and the temperature sensor.
The rear A/C control module is located in the upper
left side of the rear A/C evaporator housing.
OPERATION
The rear A/C control module is supplied fused bat-
tery power through the rear blower switch. The con-
trol module receives input signals from the rear A/C
blower motor switch, rear A/C temperature control,
rear temperature sensor and the rear evaporator
temperature sensor when the front A/C switch is
turned on. The rear A/C control module uses the
Fig. 4 Rear A/C Condenser Fan Relay
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. 5 Rear A/C Control Module
1 - REAR A/C CONTROL MODULE
2 - MOUNTING TABS
3 - WIRE HARNESS CONNECTOR
24 - 28
CONTROLS - REAR
VA
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