Chevrolet Sonic Repair Manual: Cooling Fan Description and Operation (LUV)
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
Low Speed Operation
The ECM applies ground at the FAN 1 control circuit for the coil side of the cooling fan relay. The energized cooling fan relay completes a ground, through the switch side of the relay, for the coils of the cooling fan low speed relay and the cooling fan speed control relay. The speed control relay activates and supplies B+ to the coil side of the cooling fan high speed relay. The high speed relay remains inactive because the ECM is not commanding the FAN 2 control circuit ON. The energized low speed relay switch closes to supply B+ through the internal low speed resistor of the engine cooling fan motor. The result is cooling fan operation at a reduced speed.
Medium Speed Operation
The ECM applies ground at the FAN 2 control circuit for the coil side of the cooling fan high speed, and medium speed relays. The high speed relay remains inactive because the ECM is not commanding the FAN 1 control circuit ON. The energized medium speed relay switch closes to supply B+ through the internal medium speed resistor of the engine cooling fan motor. The result is cooling fan operation at a medium speed.
High Speed Operation
The ECM applies ground at the FAN 1 control circuit for the coil side of the cooling fan relay. The energized cooling fan relay completes a ground, through the switch side of the relay, for the coil of the cooling fan speed control relay. The energized speed control relay switch closes to supply B+ to the coil side of cooling fan high speed relay. Simultaneously, the ECM applies ground at the FAN 2 control circuit for the coil side of the cooling fan high speed relay. The energized high speed relay switch closes to supply B+ directly to the engine cooling fan motor, by-passing the fans internal resistors. The result is cooling fan operation at full speed.
Radiator Fan
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Cooling Fan Description and Operation (LWE, LUW)
System Overview
The engine cooling fan system is composed of one cooling fan, 2 relays, the engine
control module (ECM), and the associated wiring. The cooling fan assembly includes
1̴ ...
Other materials:
Where Are the Airbags?
The driver frontal airbag is in the center of the steering wheel.
The front outboard passenger frontal airbag is in the passenger side instrument
panel.
The driver knee airbag, if equipped, is below the steering column. The front
outboard passenger knee airbag, if equipped, is below the gl ...
Battery Disconnect Warning
Warning: Unless directed otherwise, the ignition and start switch
must be in the OFF or LOCK position, and all electrical loads must be OFF before
servicing any electrical component. Disconnect the negative battery cable to
prevent an electrical spark should a tool or equipment come in c ...
Battery Inspection/Test
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic
procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic
catego ...
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