Suzuki XL7 2007 Service Manual page 1818

7A-4 Heating, Ventilation and Air Conditioning:
The HVAC control module uses a range of 0-255 counts
to index the actuator position. The door position signal
voltage is converted to a 0-255 count range. When the
module sets a commanded, or targeted, value, one of
the control circuits is grounded. As the actuator shaft
rotates the changing position signal is sent to the
module. Once the position signal and the commanded
value are the same, the module removes power from
both control circuits.
Auxiliary Air Temperature Actuator
The auxiliary air temperature actuator is a 5-wire bi-
directional electric motor that incorporates a feedback
potentiometer. Low reference, 5-volt reference, position
signal, and 2 control circuits enable the actuator to
operate. The control circuits use either a 0 or 12-volt
value to coordinate the actuator movement. When the
actuator is at rest, both control circuits have a value of 0
volts. In order to move the actuator, the auxiliary HVAC
control module grounds one of the control circuits while
providing the other with 12 volts. The control module
reverses the polarity of the control circuits to move the
actuator in the opposite direction. When the actuator
shaft rotates, the potentiometers adjustable contact
changes the door position signal between 0-5 volts.
The auxiliary HVAC control module uses a range of 0-
255 counts to index the actuator position. The door
position signal voltage is converted to a 0-255 count
range. When the module sets a commanded, or
targeted, value, one of the control circuits is grounded.
As the actuator shaft rotates, the changing position
signal is sent to the module. Once the position signal
and the commanded value are the same, the module
grounds both control circuits.
Condition
When the HVAC module A/C and
RECIRCULATION buttons are
pressed simultaneously.
At start up with the engine off less
than 2 hours
At start up with the engine off more
than 2 hours
Vehicle speed above 32 km/h (20
mph) for a minimum of 80 seconds
Sensor ambient temperature
reading is less than the last
displayed value
When the ambient air decreases.
Air Temperature Sensors
The air temperature sensors are a 2-wire negative
temperature co-efficient thermistor. The vehicle uses the
following air temperature sensors:
• Ambient Air Temperature Sensor
• Inside air temperature sensor assembly
• Sunload Sensor
• Upper air temperature sensor
• Lower air temperature sensor
A signal and low reference circuit enables the sensor to
operate. As the air temperature surrounding the sensor
increases, the sensor resistance decreases. The sensor
signal voltage decreases as the resistance decreases.
The sensor operates within a temperature range
between −40 to +87.5°C (−40 to +190°F). The sensor
signal varies between 0-5 volts.
The input of the duct air temperature sensors are
different from the ambient and inside sensors. The
HVAC control module converts the signal to a range
between 0-255 counts. As the air temperature increases
the count value will decrease.
If the HVAC control module detects a malfunctioning
sensor, then the control module software will use a
defaulted air temperature value. The default value for
the inside air temperature sensor will be displayed on
the scan tool. The default value for the duct air
temperature sensors will not be displayed on the scan
tool. The scan tool parameter for the duct air
temperature sensors are the actual state of the signal
circuit. The default action ensures that the HVAC system
can adjust the inside air temperature near the desired
temperature until the condition is corrected.
The ambient air temperature sensor mounts underhood
and can be affected by city traffic, by idling, and by
restarting a hot engine. Therefore, the HVAC control
module filters the value of the ambient air temperature
sensor for temperature display. The ambient air
temperature value is updated under the following
conditions:
Updates temperature display instantly
Displays last stored temperature unless temperature has decreased. The
outside air temperature reading is always instantly updated if ambient air
temperature has decreased.
Displays actual outside temperature
Updates temperature display at a slow filtered rate
Displays actual outside temperature
Updates temperature display rapidly
Display