GMC chervolet camaro 1999 Service Manual page 129

1-38 HVAC System - Manual
Mode Control Vacuum Valve Positions
1 OFF
2 MAXA/C
3 NORMALA/C
4
Bl-LEVEL A/C
5
VENT
6 HEATER
7
HEATER/DEFROST BLEND
8 DEFROSTER
A vacuum operates most of the air distribution system.
Electrical power operates the blower motor.
The.engine vacuum is routed through the
following areas:
• The vacuum check valve
• The control vacuum selector
• The vacuum tank
The vacuum check valve prevents vacuum loss.
Heavy acceleration or steep uphill traveling may cau~e
vacuum loss.
Vacuum applied to a vacuum actuator moves the air
door to the air door's correct position.
HVAC
Preliminary Inspection
1. Inspect the vacuum lines at the engine and
vacuum check valve for a proper connection.
2. Disconnect the vacuum line that leads to the
engine at the vacuum check valve.
3. Start the engine.
4. Inspect for vacuum presence. If no vacuum is
present, repair as required.
5. Disconnect the vacuum line that leads to the
vacuum tank at the vacuum check valve.
6. Use a hand vacuum pump in order to apply
vacuum to the vacuum line that leads to the
vacuum tank If the JtacuumJioeanolbol~replace
the vacuum line and/or the vacuum tank.
7. Disconnect the vacuum line that leads to the
control at the vacuum check valve.
8. Apply vacuum to the check valve port. If the
vacuum does not hold, replace the vacuum
check valve.
9. Quickly rotate the temperature control from full
COLD to full HOT several times.
10. Listen for the temperature valve to seat in both
positions.
If the sound indicates that the temperature valve
is not fully seating or opening, inspect the
temperature control cable for proper operation. If
the problem persists, ensure that the temperature
valve door operates freely with the blower off.
11. Ensure that the vacuum line seals are positioned
correctly at the vacuum line multi-connector that is
located above the right-hand sound
insulator panel.
12. Perform the diagnosis.
Diagnostic Aid Chart
Checks
Action
Apply vacuum to the red vacuum line. Air flow is diverted to the instrument panel outlets only.
Apply vacuum to the yellow Air flow is diverted to the side window defogger and floor outlets.
vacuum line.
Apply vacuum to the purple Air flow is diverted to the side window defogger, floor and instrument panel outlets.
vacuum line.
Apply vacuum to the green Air flow is diverted to the windshield and side window defogger outlets.
vacuum line.
Apply vacuum to the orange Air flow is diverted to the blower motor assembly air noise increase.
vacuum line.
Apply vacuum to no vacuum lines. Air flow is diverted to all outlets except the instrument panel.
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