GMC Chevrolet Camaro 1998 Service Manual page 234

1-124 HVAC System - Manual
MAX
The following actions occur when the knob is in the
MAX position:
• An A/C request signal is sent to the PCM.
• The blower motor operates in one of four blower
motor speed control settings.
• Air is discharged only from the instrument panel
air outlets.
• In order to provide MAX A/C, most of the air
entering the HVAC module is taken from the
vehicle interior (re-circulated). This interior air is
cooler than the outside air. MAX is the only setting
at which the air is re-circulated.
Use the MAX setting when the following
conditions exist:
• High temperature
• High humidity
• The outside air has an objectionable odor
A/C
The A/C setting functions the same as the MAX
setting, except that only outside air enters the HVAC
module. There may be a slight reduction of blower
noise compared to the MAX setting because the
re-circulation valve (door) is closed.
Bl-LEVEL A/C
The following actions occur when the knob is in the
Bl-LEVEL A/C position:
• An A/C request signal is sent to the PCM in order
to allow the blower motor to operate in one of
four settings.
• Only outside air enters the HVAC module.
• Air is distributed through the instrument panel
outlets and the floor outlets ..
• A small amount of air is distributed to the defrost
01,Jtlet.
VENT
The VENT setting does not activate an A/C request
signal but allows the blower motor to operate normally.
The VENT setting is one of two economy settings
(other than OFF) in which there is no A/C request
signal. Air is discharged through the instrument panel
outlets only.
HEATER
The HEATER setting functions the same as the VENT
setting, except that most of the air is discharged through
the floor outlets with a small amount of air discharged
through the defroster outlets. Use the HEATER setting
for cold weather operation unless windshield or side
window defogging/defrosting is required.
DEFROST/BLEND
The following actions occur in the DEFROST/BLEND
setting:
• The blower motor operates.
• An A/C request signal is sent to the PCM.
• Air is discharged through the defroster and floor
air outlets.
HVAC
The DEFROST/BLEND setting provides greater
passenger comfort than the DEFROST setting, but it
is not as effective in defogging/defrosting the
windshield and· side windows.
DEFROST
The DEFROST setting functions the same as the
DEFROST/BLEND setting except that most of the air
is discharged through the defroster outlets. A small
amount of air goes through the heater and side
windows defoggers.
Blower Motor Speed Control
• The blower motor runs in all mode positions
· except the OFF position when the ignition switch
is in the RUN position.
• The blower motor speed is controlled by a
four-position electrical blower motor speed control
switch. The switch is located at the left side of
the control.
• The blower motor speed control switch provides a
choice of the following speeds:
• Low
• Medium (two settings)
• High
• Power is routed from the HVAC fuse in the fuse
block to the mode control switch.
• The mode control switch breaks the circuit when
the switch is in the OFF position. The switch
closes the circuit in all other positions.
• From the mode control switch the circuit goes to
the blower motor speed control switch.
• When the blower motor speed control switch is
turned to the LOW setting, voltage is conducted
··to the resistor. At the resistor, the voltage passes
through all three resistors and is reduced to
provide the low blower motor speed.
• When the blower switch is in either of the two
medium speed positions, the switch closes.
This action sends voltage through one or two of
the resistors. Because the current follows the path
of least resistance, the circuit branch that leads
directly to all three resistors becomes ineffective.
At this point the current bypasses either one
or two resistors, depending upon which medium
speed position is selected. The reduced resistance
increases the current flow and blower
motor speed.
• When the blower motor switch is turned to the
HIGH setting, the action energizes the high blower
relay. Power is taken from a separate circuit
that is protected by a fusible link. The separate
power circuit is hot at all times. The circuit has the
capacity to handle the current demands of the
blower motor at high speed.
• The circuit to the blower motor is completed to
ground at the instrument panel through the
instrument panel wiring harness.
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