Sprinter 3500 V6-3.0L DSL Turbo VIN 45 (2007)
Condenser Fan Motor Relay: Description and Operation
Controls - Front
Description
DESCRIPTION
All models use an International Standards Organization (ISO)-type condenser fan relay (1). The condenser fan relay is a electromechanical device that
switches battery current to the A/C condenser fan motors. The condenser fan relay consists of a molded plastic housing with an integral connector (2)
which connected to the vehicle electrical system by four terminals. Relays conforming to the ISO specifications have common current capacities,
terminal functions and patterns. The condenser fan relay coil is energized by the powertrain control module (PCM) or engine control module (ECM)
(depending on engine application) whenever there is a demand for A/C.
The condenser fan relay is located behind the condenser fan shroud in the front of the engine compartment.
Operation
OPERATION
The condenser fan relay is an electromechanical switch that uses a low current input from the powertrain control module (PCM) or engine control
module (ECM) to control current flow to the A/C condenser fan motors. 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 fused battery current to flow to
the condenser fan motors.
When the relay coil is de-energized, spring pressure 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 electromagnetic interference that can be generated as the
electromagnetic field of the relay coil collapses.
The inputs and outputs of the condenser fan relay include:
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The common feed terminal (30) receives battery current at all times.
-
The coil ground terminal (86) receives a ground through the condenser fan relay control circuit only when the PCM/ECM electronically pulls the
circuit to ground.
-
The coil battery terminal (85) receives battery current at all times.
-
The normally open terminal (87) provides a battery current output to the A/C condenser fan motor circuits only when the condenser fan relay coil
is energized.
-
The normally closed terminal (87A) is not connected to any circuit in this application, but provides a battery current output only when the
condenser fan relay coil is de-energized.
The condenser fan relay cannot be adjusted or repaired and must be replaced if inoperative or damaged. Refer to the appropriate wiring information for
diagnosis and testing of the ISO-standard relay and for complete HVAC wiring diagrams.
