Suzuki XL7 2007 Service Manual page 1819

Sunload Sensor
The sunload sensor is a 2-wire photo diode. The vehicle
uses left and right sunload sensors. The 2 sensors are
integrated into the sunload sensor assembly. Low
reference and signal circuits enable the sensor to
operate. As the light shining upon the sensor gets
brighter, the sensor resistance increases. The sensor
signal decreases as the resistance increases. The
sensor operates within an intensity range between
completely dark and bright. The sensor signal varies
between 0-5 volts. The HVAC control module converts
the signal to a range between 0-255 counts.
The sunload sensor provides the HVAC control module a
measurement of the amount of light shining on the
vehicle. Bright, or high intensity, light causes the vehicles
inside temperature to increase. The HVAC system
compensates for the increased temperature by diverting
additional cool air into the vehicle.
If the HVAC control module detects a malfunctioning
sensor, then the control module software will use a
defaulted sunload value. This value will not be displayed
on the scan tool. The default action ensures that the
HVAC system can adjust the inside air temperature near
the desired temperature until the condition is fixed. The
scan tool parameter for the sunload sensor is the actual
state of the signal circuit.
A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire
piezoelectric pressure transducer. A 5-volt reference,
low reference, and signal circuits enable the sensor to
operate. The A/C pressure signal can be between 0-5
volts. When the A/C refrigerant pressure is low, the
signal value is near 0 volts. When the A/C refrigerant
pressure is high, the signal value is near 5 volts.
The A/C refrigerant pressure sensor protects the A/C
system from operating when an excessively high or low
pressure condition exists. The engine control module
(ECM) disables the compressor clutch under the
following conditions:
• The A/C high side pressure is more than 2 929 kPa
(425 psi).
• The clutch will be enabled after the high side pressure
decreases to less than 1 376 kPa (200 psi).
• A/C low side pressure is less than 269 kPa (39 psi).
• The clutch will be enabled or will allow engagement
again after the low side pressure increases to more
than 296 kPa (43 psi).
Evaporator Low Ambient Protection
The refrigerant temperature at the temperature sensor
on the evaporator case controls cycling of the
compressor clutch to prevent freezing of the evaporator
core. The compressor is disabled when the temperature
goes below 3°C (37°F) and vehicle speed is greater than
8 km/h (5 mph). The compressor is enabled when the
temperature exceeds 4°C (40°F). The minimum cycling
time off is 4 seconds.
Heating, Ventilation and Air Conditioning:
Heating and A/C Operation
The purpose of the heating and A/C system is to provide
heated and cooled air to the interior of the vehicle. The
A/C system will also remove humidity from the interior
and reduce windshield fogging. The vehicle operator can
determine the passenger compartment temperature by
adjusting the air temperature control. Regardless of the
temperature setting, the following can effect the rate that
the HVAC system can achieve the desired temperature:
• Recirculation
• Difference between inside and desired temperature
• Difference between ambient and desired temperature
• Blower motor speed setting
• Mode setting
The vehicle operator can activate the A/C system by
pressing the A/C switch. The A/C system can operate
regardless of the temperature setting.
The engine control module (ECM) will operate the A/C
system automatically in FRONT DEFROST mode to
help reduce moisture inside the vehicle. The A/C LED
will not illuminate unless the driver presses the A/C
request switch on the HVAC control module. The A/C
system maybe running without the A/C LED indicator
illuminated when in FRONT DEFROST mode. The
HVAC system uses a compressor that incorporates a
thermal switch that opens once the compressor
temperature exceeds 211-217°C (380-454°F) creating
an open circuit. The following conditions must be met in
order for the ECM to turn on the compressor clutch:
• BCM
– Battery voltage between 11-16 volts
– A/C request from the HVAC control module
• ECM
– Engine coolant temperature (ECT) is greater than
117°C (243°F).
– Engine speed is less than 4,760 RPM.
– A/C pressure is between 2,929-2,706 kPa (425-39
psi).
Once engaged, the compressor clutch will be
disengaged for the following conditions:
• Throttle position is 100 percent
• A/C pressure is more than 2,929 kPa (425 psi).
• A/C pressure is less than 269 kPa (39 psi).
• ECT is more than 120°C (248°F).
• Engine speed is more than 6240 RPM.
• Transmission shift
• ECM detects excessive torque load.
• ECM detects insufficient idle quality.
• ECM detects a hard launch condition.
When the compressor clutch disengages, the
compressor clutch diode protects the electrical system
from a voltage spike.
7A-5