Neon L4-2.0L DOHC (1996)
Radiator Fan Relay: Description and Operation
Description of Trouble Codes
High Speed Fan Relay Control Circuit
Name of Code:
High Speed Fan Control Relay Circuit
When Monitored:
With the ignition key in the run position and battery voltage above 10 volts.
Set Condition:
An open or shorted condition is detected in the high speed fan relay control circuit.
Theory of Operation:
The high speed fan relay controls the high speed operation of the radiator fans. The relay is located in the power distribution center. One side of
the relay control coil is supplied with 12 volts when the ignition switch is turned to the run position. The circuit is completed when the other side
of the relay coil is grounded by the powertrain control module (PCM). The PCM grounds the relay control circuit when the engine coolant
temperature is too high and removes the ground when the temperature is acceptable.
Possible Causes:
-
Relay coil open or shorted
-
Fused ignition switch output circuit open
-
High speed fan relay control circuit is open or shorted
-
Inoperative circuit driver in powertrain control module
Rad Fan Control Relay Circuit
Name of Code:
Rad Fan Control Relay Circuit
When Monitored:
With the ignition key on, battery voltage greater than 10 volts, and the PCM requests the fans to be turned on.
Set Condition:
An open or shorted condition is detected in the Radiator Fan Control Relay Circuit.
Theory of Operation:
The solid state radiator fan relay controls the operation of the radiator fans. One connector of the relay is supplied with fused B(+) to power the
fans. This same B(+) connection powers the internal electronics in the relay. The chassis ground connection (physical attachment to the chassis) on
the relay provides a heat sink for the relay and a ground for the internal electronics. The ground connection from the relay connector is a redundant
ground for the internal relay electronics. If the relay attachment to the chassis becomes loose or corroded the relay could fail due to its inability to
dissipate heat through the chassis attachment. when the relay control circuit is grounded by the PCM, current flows through the relay to the fans.
As the engine temperature rises to a preset level, the PCM will start sending a "Pulse Width Modulated" (PWM) ground signal to the relay. The
dwell time of the signal will increase or decrease from 30% to 100% based on the engine coolant temperature and A/C pressures. this method of
controlling the fans provides an infinitely variable fan speed.
Possible Causes:
-
Relay Failure
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Fused B(+)
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Radiator fan relay control circuit open or shorted
-
PCM Failure
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Connector terminals
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Connector Wires