Dakota Quad Cab 2WD V8-4.7L VIN N (2001)
Wiper Relay: Description and Operation
The wiper relay (or intermittent wipe relay) is located in the Power Distribution Center (PDC) near the battery in the engine compartment. See the fuse
and relay layout label affixed to the inside surface of the PDC cover for wiper relay identification and location. The wiper relay is a conventional
International Standards Organization (ISO) micro relay. Relays conforming to the ISO specifications have common physical dimensions, current
capacities, terminal patterns, and terminal functions. The relay is contained within a small, rectangular, molded plastic housing. The relay is connected to
all of the required inputs and outputs through its PDC receptacle by five male spade-type terminals that extend from the bottom of the relay base. The
ISO designation for each terminal is molded into the base adjacent to the terminal. The ISO terminal designations are as follows:
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30 (Common Feed) - This terminal is connected to the movable contact point of the relay.
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85 (Coil Ground) - This terminal is connected to the ground feed side of the relay control coil.
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86 (Coil Battery) - This terminal is connected to the battery feed side of the relay control coil.
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87 (Normally Open) - This terminal is connected to the normally open fixed contact point of the relay.
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87A (Normally Closed) - This terminal is connected to the normally closed fixed contact point of the relay.
The wiper relay cannot be adjusted or repaired. If the relay is damaged or faulty, it must be replaced.
The wiper relay (or intermittent wipe relay) is an electromechanical switch that uses a low current input from the Central Timer Module (CTM) to
control a high current output to the low speed brush of the wiper motor. The movable common feed contact point is held against the fixed normally
closed contact point by spring pressure. When the relay coil is energized, an electromagnetic field is produced by the coil windings. This electromagnetic
field draws the movable relay contact point away from the fixed normally closed contact point, and holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring pressure returns the movable contact point back against the fixed normally closed contact point. A
resistor or diode is connected in parallel with the relay coil in the relay, and helps to dissipate voltage spikes and electromagnetic interference that can be
generated as the electromagnetic field of the relay coil collapses.
The wiper relay terminals are connected to the vehicle electrical system through a connector receptacle in the Power Distribution Center (PDC). The
inputs and outputs of the wiper relay include:
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The common feed terminal (30) is connected to the wiper motor low speed brush through the wiper control circuitry of the multi-function switch
on the steering column. When the wiper relay is de-energized, the common feed terminal is connected to the wiper park switch output through the
CTM on the front wiper park switch sense circuit. The wiper park switch output may be battery current (wipers are not parked), or ground (wipers
are parked). When the wiper relay is energized, the common feed terminal of the relay is connected to battery current from a fuse in the Junction
Block (JB) through a fused ignition switch output (run-acc) circuit.
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The coil ground terminal (85) is connected to the relay control output of the CTM through the wiper relay control circuit. The CTM controls the
ground path for this circuit internally to energize or de-energize the wiper relay based upon its programming, inputs from the wiper and washer
control circuitry of the multi-function switch, and inputs from the wiper motor park switch.
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The coil battery terminal (86) is connected to battery current from a fuse in the Junction Block (JB) through a fused ignition switch output
(run-acc) circuit whenever the ignition switch is in the ON or Accessory positions.
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The normally open terminal (87) is connected to battery current from a fuse in the Junction Block (JB) through a fused ignition switch output
(run-acc) circuit whenever the wiper relay control coil is energized by the CTM. This circuit provides fused ignition switch output (run-acc)
current to the wiper motor low speed brush only when the wiper relay control coil is energized.
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The normally closed terminal (87A) is connected to the output of the wiper motor park switch through the CTM on the front wiper park switch
sense circuit. This circuit provides battery current (wipers are not parked) or ground (wipers are parked) to the wiper motor low speed brush
whenever the wiper relay control coil is de-energized and the OFF position of the wiper control circuitry within the multi-function switch is
selected.
The wiper relay can be diagnosed using conventional diagnostic tools and methods.
