Liberty Sport 4WD L4-2.4L VIN 1 (2002)
Trailer Lighting Relay: Description and Operation
Fig.64 Trailer Tow Relays
TRAILER TOW RELAY
The trailer tow relays are located in a connector bank above the right rear wheelhouse and behind the quarter trim panel on vehicles equipped with
the optional factory-installed trailer towing package. Four individual relays are used, one each for fused ignition switch output (run), brake lamps,
right turn signal, and left turn signal outputs to a trailer through the rear body wiring and connectors. The trailer tow relays are conventional
International Standards Organization (ISO) micro relays (Fig. 64).
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 and is connected to all of the required inputs and outputs by five integral
male spade-type terminals that extend from the bottom of the relay base.
The trailer tow relays cannot be adjusted or repaired and, if faulty or damaged, the inoperative relay must be replaced.
The trailer tow relays are electromechanical switches. The relays each use an input from the circuit that they isolate from the trailer wiring to
control a high current output to the trailer. 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 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 terminals of each trailer tow relay are connected to the vehicle electrical system through a connector bank in the rear lighting wire harness
above the right rear wheelhouse. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and
connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire
harness connectors, splices and grounds. The trailer tow relays can be diagnosed using conventional diagnostic tools and methods.
