GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Functional Check

Functional Check without D55

The following operational test sequence aids in determining whether the following HVAC system is functioning properly:

    • Electrical
    • Air distribution
    • Vacuum
    • Refrigeration

Ensure that the ambient air temperature is above 5°C (41°F). Ensure that the engine is warmed to the normal operating temperature.

Function Test for System

Action

Normal Result

Start the engine.
  • The engine warms in order to perform the test.

Press the OFF button.
  • With the blower OFF, the display shows the following information:
    • The set temperature
    • OFF
    • The outside temperature

Press the AUTO button.
    • The system turns ON.
    • The display shows the AUTO fan and AUTO mode.

Set the temperature at 15°C (60°F).
    • The blower is at high speed.
    • Cold air flows from the A/C outlets.

Press the ECON button.
    • The RECIRC LED turns OFF.
    • ECON is displayed.

Press the RECIRC button.
    • The RECIRC LED is ON.
    • The blower noise slightly increases.

Press the AUTO button.
  • AUTO is displayed.

Set the temperature to 32°C (90°F).
    • Hot air flows from the heater outlets.
    • The RECIRC LED is OFF.

Press the DEFOG button (if equipped).
    • Air flows from the heater outlets.
    • The RECIRC LED is OFF.

Press the RECIRC button.
    • The RECIRC LED is ON.
    • The blower noise increases slightly.

Press the DEFROST button.
    • Air flows from the windshield outlets.
    • The RECIRC LED is OFF.

Press the FAN down button 2 times.
  • With the blower at low speed, LO is displayed.
  1. Set the temperature to 24°C (75°F).
  2. Press the AUTO button.

AUTO is displayed.

Press the PASS TEMP on the jet to MAX WARM.

The air from the right side A/C outlets should be warmer than the driver side outlets.

Functional Check with D55

The following operational test sequence aids in determining whether the following HVAC system is functioning properly:

    • Electrical
    • Air distribution
    • Vacuum
    • Refrigeration

Ensure that the ambient air temperature is above 5°C (41°F). Ensure that the engine is warmed to the normal operating temperature.

Function Test for System

Action

Normal Result

Start the engine.
  • The engine warms in order to perform the test.

Press the OFF button.
  • With the blower OFF, the display shows the following information:
    • The set temperature
    • OFF
    • The ambient temperature

Press the AUTO button.
    • The system turns ON.
    • The display shows the following information:
       - The fan icon
       - The mode arrows
       - The set temperature
       - AUTO

Set the temperature at 15°C (60°F).
    • With the blower at high speed, cold air flows from the A/C outlets.
    • The RECIRC LED is ON.

Press the FAN down button 2 times.
  • The blower is at low speed.

Press the AUTO button.
  • The blower is at high speed.

Press the MODE up button.
  • Air flows from the heater outlets and from the windshield outlets.

Press the MODE down button.
  • Air flows from the A/C outlets.

Press the MODE down button.
  • Air flows from the A/C outlets and from the heater outlets.

Press the MODE down button.
  • Air flows from the heater outlets.

Press the RECIRC button.
    • The blower noise increases slightly.
    • The RECIRC LED is ON.

Press the DEFROST button.
    • Air flows from the windshield outlets.
    • The blower is at high speed.

Set the temperature to 32°C (90°F).
  • Hot air flows from the windshield outlets.
  1. Set the temperature to 24°C (75°F).
  2. Press the AUTO button.
  • AUTO is displayed.

Press the PASS TEMP up button 4 times.
    • Air from the right side A/C outlets should be warmer than the driver side outlets.
    • The display shows 3.5 red bars.