Suzuki XL7 2007 Service Manual page 1854

7A-40 Heating, Ventilation and Air Conditioning:
Blower Motor Malfunction
Diagnostic Instructions
• Perform the "Diagnostic System Check - Vehicle Diagnostic Information: " prior to using this diagnostic procedure.
• "Strategy Based Diagnosis: "
• "Diagnostic Procedure Instructions - Vehicle Diagnostic Information: "
Diagnostic Fault Information
Perform the "Diagnostic System Check - Vehicle Diagnostic Information: " prior to using this diagnostic procedure.
Circuit
Blower Motor Speed Control circuit at the
blower motor control processor
Battery Positive Voltage circuit at the blower
motor control processor
Ground circuit of the blower motor control
processor
Blower Motor Low Reference circuit
(between motor and control processor)
1. Blower Motor Inoperative
2. Blower Motor Always On
Circuit/System Description
Blower Motor Control Processor
The blower motor control processor is an interface
between the HVAC control module and the blower motor.
The blower motor speed control, battery positive and
ground circuits enable the control processor to operate.
The HVAC control module provides a pulse width
modulation (PWM) signal to the blower motor speed
control processor in order to command the blower motor
speed. The processor supplies 12 volts to the blower
motor through the blower motor voltage supply circuit.
The control processor uses the blower motor ground or
low reference as a low side control to adjust the blower
motor speed.
Air Speed
The blower motor forces air to circulate within the
vehicles interior. The vehicle operator determines the
blower motors speed by placing the blower motor switch
in a desired speed position. The blower motor will only
operate if the blower motor switch is in any position other
than OFF, and the ignition switch is in the RUN position.
Once a blower speed is selected, the blower speed
remains constant until a new speed is selected.
As the requested blower speed increases, the following
conditions occur:
• The HVAC control module increases the amount of
time that the blower motor speed control circuit is
modulated to ground.
• The voltage and duty cycle, measured between the
blower motor speed control circuit and ground,
decrease.
Short to Open/High
Ground Resistance
1, 2 1
— 1
— 1
— 1
As the requested blower speed decreases, the following
conditions occur:
• The HVAC control module decreases the amount of
time that the blower motor speed control circuit is
modulated to ground.
• The voltage and duty cycle, measured between the
blower motor speed control circuit and ground,
increase.
Diagnostic Aids
Be sure the blower motor housing is not shorted to a
grounded surface causing the blower motor to always be
on in high speed.
Reference Information
Schematic Reference
"HVAC Schematics"
Connector End View Reference
"HVAC Connector End Views"
Description and Operation
• "Air Delivery Description and Operation"
• "Air Temperature Description and Operation"
Electrical Information Reference
• "Circuit Testing: "
• "Connector Repairs: "
• "Testing for Intermittent Conditions and Poor
Connections: "
• "Wiring Repairs: "
Scan Tool Reference
• "Scan Tool Output Controls - HVAC - Automatic"
• "Scan Tool Data List - HVAC - Automatic"
• "Scan Tool Data Definitions - HVAC - Automatic"
Signal
Short to Voltage
Performance
1, 2
—
—
—
—
—
—
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