Chart 1C-3 Improper Air Delivery

Diagnostic Chart:

Air Delivery Vacuum Distribution Table:

Wiring Diagram:

CIRCUIT DESCRIPTION

Air Delivery

With the ignition switch in "RUN," voltage is applied through I/P fuses #20 and #33 to the H-A/C control. The operating mode of the system is determined by buttons on the front panel. Ground signals determine which air valves are to be operated as well as the position of the temperature valve.

The vacuum/electric solenoid contains the solenoid valves that control the vacuum actuators. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the vent position.

Air Delivery

H-A/C Control

With the ignition switch in "RUN," voltage is applied through I/P fuses #20 and #33 to the H-A/C control. The operating mode of the system is determined by buttons on the front panel. Ground signals determine which air valves are to operated as well as the position of the temperature valve.

Vacuum/Electric Solenoid

The vacuum/electric solenoid contains the solenoid valves that control the vacuum actuators. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the vent position.

Recirculation Valve

The recirculation valve closes off most of the outside air inlet, so that the air from the inside of the vehicle is recirculated through the A/C system for maximum cooling. The outside air inlet is partially closed when vacuum is applied to the actuator. When the air inlet valve actuator is vented, the recirculation valves close off the in-car air inlet which allows outside air to be drawn into the vehicle.

Temperature Valve

The temperature valve determines how much air flows through the heater core, which determines the temperature of the air to the outlets. It is moved by the temperature valve electric actuator. The position of the valve is determined by the temperature selected at the H-A/C control.

DEF/Heater

The DEF/heater valve determines whether air flow will be directed to the windshield defrost outlets. With vacuum applied to the gray hose at the defroster valve actuator, the valve is positioned to allow air flow to the windshield defrost outlets, with some bleed to the heater outlet.

Upper/Lower Mode

The upper/lower mode valve can assume three positions and is operated by a bi-directional vacuum port which can move the valve to either of two positions. If no vacuum is applied to either vacuum port, the valve is in mid-position. Air flow with the valve in mid-position will be delivered to the panel outlets and the floor outlets (Bi-Level). When the upper/lower solenoid (#3) (tan vacuum hose) is operated, the valve is positioned to direct air flow to the A/C outlets. When the upper/lower solenoid (#4) (red vacuum hose) is operated, the valve is positioned to direct air flow to the heater outlets and defroster outlets.

Temperature Control

Two temperature variable resistors (sensors) are connected to the H-A/C control to provide in-car and outside temperature information. These devices are thermistors which decrease in resistance as the temperature of the device increases. The one exception to this is the solar sensor, which is a photo diode. The photo diode output decreases with increasing light intensity.

Circuits within the H-A/C control use the input from the in-car sensor and the sun load sensor and the set temperature selected by the driver to determine whether the air should be heated or cooled to bring the inside of the vehicle to the selected temperature. The input from the ambient temperature sensor is used to determine the amount of heating or cooling required to bring the temperature inside the vehicle to the selected value as quickly as possible.

DIAGNOSTIC AIDS

1. If the temperature valve electric actuator is displaced from its proper position, it will automatically calibrate itself to the proper position if the battery power is removed from the H-A/C control. To recalibrate the temperature valve actuator, remove and install I/P fuse 33.

2. Make sure that ground G207 is clean and tight.

3. Check I/P fuse 33. If open, check for a short to ground in CKT 40.

4. Check I/P fuse 20. If open, check for a short to ground in CKT 241.

5. Check for normal operation of engine vacuum check valve.

With engine warm and running in idle:

6. Check manifold vacuum at the violet hose from the vacuum tank to the electric solenoid.

7. Check for vacuum at the violet hose from the vacuum tank to the electric solenoid.

8. Check that the vacuum hoses from the electric solenoid to the vacuum actuators are connected and in good condition.

9. Check for a broken (or partially broken) wire inside of the insulation which could cause system failure but prove "GOOD" in a continuity/voltage check. Refer to Diagrams / Diagnostic Aids. Diagnostic Aids

10. Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems. Refer to Diagrams / Diagnostic Aids. Diagnostic Aids

Vacuum Diagnosis

1. Check vacuum supply to vacuum/electric solenoid (black vacuum hose) while engine is running.

- Vacuum should be approximately 38 to 43 cm Hg (15 to 16 inch Hg) with engine running.

- Vacuum should remain at approximately 38 to 43 cm Hg (15 to 16 inch Hg) when engine is turned off.

2. Test each vacuum actuator by disconnecting the vacuum hose and applying vacuum directly to the actuator. Repair or replace as necessary.

3. Reconnect all vacuum and electrical connections. Run engine and cycle through the operating modes and full temperature range of the H-A/C control while observing the vacuum actuators.

- Check for vacuum to the vacuum actuators by noting vacuum actuator position. When vacuum is applied, the actuator will retract, refer to the Air Delivery Vacuum Distribution Table.

- If a vacuum actuator retracts when it should not, replace the H-A/C control, after performing the diagnostics on the Diagnostic Chart 1C-3.

- If a vacuum actuator does not retract when it should, check for vacuum leaks, collapsed vacuum hoses, binding valves or bad connections at the vacuum/electric solenoid. If OK, replace the vacuum/electric solenoid.