Dodge ZB 2005 Service Manual page 1043

24 - 14 CONTROLS
A/C COMPRESSOR CLUTCH
RELAY
DESCRIPTION
The A/C clutch relay (Fig. 8) is a International
Standards Organization (ISO) micro-relay. Relays
conforming to the ISO specifications have common
physical dimensions, current capacities, terminal
functions and patterns. The ISO micro-relay terminal
functions are the same as a conventional ISO relay.
However, the ISO micro-relay terminal pattern (or
footprint) is different, the current capacity is lower,
and the physical dimensions are smaller than those
of the conventional ISO relay.
The A/C clutch relay is located in the power distri-
bution center (PDC) in the engine compartment.
Fig. 8 A/C Compressor Clutch Micro-Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
OPERATION
The A/C clutch relay is an electromechanical
switch that uses a low current input controlled by
the powertrain control module (PCM) to control the
high current output to the A/C clutch field coil. 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 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 A/C clutch relay terminals are connected to
the vehicle electrical system through a receptacle in
the power distribution center (PDC). The inputs and
outputs of the A/C clutch relay include:
• The common feed terminal (54) receives a bat-
tery current input from fuse 20 (15 amp) in the PDC
through a fused B(+) circuit at all times.
• The coil ground terminal (51) receives a ground
input from the PCM through the compressor clutch
relay control circuit only when the PCM electroni-
cally pulls the control circuit to ground.
• The coil battery terminal (53) receives a battery
current input from fuse 60 (15 amp) in the PDC
through a fused ignition switch output (run-start) cir-
cuit only when the ignition switch is in the On or
Start positions.
• The normally open terminal (50) provides a bat-
tery current output to the compressor clutch coil
through the compressor clutch relay output circuit
only when the compressor clutch relay coil is ener-
gized.
• The normally closed terminal (52) is not con-
nected to any circuit in this application, but provides
a battery current output only when the compressor
clutch relay coil is de-energized.
The 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 micro-relay and for com-
plete HVAC wiring diagrams.
REMOVAL
(1) Disconnect and isolate the negative battery
cable.
(2) Open the cover of the power distribution center
(PDC) located in the engine compartment (Fig. 9).
NOTE: Refer to the fuse and relay layout map on
the inside of the PDC cover for A/C clutch relay
location.
(3) Remove the A/C clutch relay from the PDC.
INSTALLATION
NOTE: Refer to the fuse and relay layout map on
the inside of the power distribution center (PDC)
cover for A/C clutch relay location.
ZB