RAM 2500 Van V8-5.2L Prop VIN 2 (2000)
Horn Relay: Description and Operation
The horn relay is a component of the Remote Keyless Entry (RKE) system only on vehicles equipped with the optional Vehicle Theft Security System
(VTSS). The horn relay is a International Standards Organization (ISO) micro-relay. The terminal designations and functions are the same as a
conventional ISO relay. However, the micro-relay terminal orientation (or footprint) is different, current capacity is lower, and the relay case dimensions
are smaller than those of the conventional ISO relay.
The horn relay is a electromechanical device that switches battery current to the horn when the horn switch grounds the relay coil. The horn relay is
located in the relay and fuse block on the driver side end of the instrument panel in the passenger compartment. If a problem is encountered with a
continuously sounding horn, it can usually be quickly resolved by removing the horn relay from the relay and fuse block until further diagnosis is
completed.
The horn relay is a International Standards Organization (ISO) micro-relay. Relays conforming to the ISO specifications have common physical
dimensions, current capacities, terminal patterns, and terminal functions. 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 horn relay cannot be repaired or adjusted and, if faulty or damaged, it must be replaced.
The ISO relay consists of an electromagnetic coil, a resistor or diode, and three (two fixed and one movable) electrical contacts. The movable (common
feed) relay contact is held against one of the fixed contacts (normally closed) by spring pressure. When the electromagnetic coil is energized, it draws the
movable contact away from the normally closed fixed contact, and holds it against the other (normally open) fixed contact.
When the electromagnetic coil is de-energized, spring pressure returns the movable contact to the normally closed position. The resistor or diode is
connected in parallel with the electromagnetic coil in the relay, and helps to dissipate voltage spikes that are produced when the coil is de-energized.
