TROUBLE SHOOTING
The self-diagnostic function provides indication of abnormal conditions in A/C control unit, related sensors and wirings. Self-diagnostic function includes an automatic control back-up, which provides substitute value(s) in case of system failure. Data link connector is located under left side of dash. Diagnostic codes can be accessed with an analog voltmeter, Multi-Use Tester (MUT) or MUT-II.
ACCESSING TROUBLE CODES
| CAUTION | Before connecting or disconnecting MUT (or MUT-II), ensure ignition is off. |
CLEARING TROUBLE CODES
Turn ignition off. Disconnect battery cable for at least 10 seconds. Reconnect battery cable, and check voltmeter. Ensure a normal code (Code 0) is displayed. When using an analog voltmeter, normal code is indicated by continuous voltmeter needle sweep pattern.
TESTING
| WARNING | To avoid injury from accidental air bag deployment, read and carefully follow all SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM procedures in appropriate AIR BAG RESTRAINT SYSTEM article in ACCESSORIES/SAFETY EQUIPMENT section below. |
- «AIR BAG RESTRAINT SYSTEM»(ref-27817) (for 3000GT)
- AIR BAG RESTRAINT SYSTEM (for Stealth)
A/C CONTROL UNIT CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See A/C CONTROL UNIT CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 53 (Back-Up Power) | At All Times | 12 |
| 107 (Ground) | At All Times | 0 |
| 108 (Power Source) | Ignition On | 12 |
| 115 (Ground) | At All Times | 0 |
| 116 (Power Source) | Ignition On | 12 |
A/C CONTROL UNIT CIRCUIT TEST
Scheme 1
POTENTIOMETER CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See POTENTIOMETER CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 56 (Blend-Air Damper) | Max. Cool Setting (1) | 0.1-0.3 |
| 56 (Blend-Air Damper) | Max. Hot Setting (1) | 4.7-5.0 |
| 57 (Mode Selector Damper) | Face Setting (1) | 0.1-0.3 |
| 57 (Mode Selector Damper) | Defrost Setting (1) | 4.7-5.0 |
| 58 (Damper Ground) | At All Times | 0 |
| 60 (Power Source) | At All Times | 4.8-5.2 |
| (1) Damper position |
POTENTIOMETER CIRCUIT TEST
IN-CAR TEMPERATURE SENSOR, AIR INLET TEMPERATURE SENSOR & EVAPORATOR THERMISTOR CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See IN-CAR TEMPERATURE SENSOR, AIR INLET TEMPERATURE SENSOR & EVAPORATOR THERMISTOR CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 55 (Air Inlet Temp. Sensor) | 77°C (25°C) (1) | 2.2-2.8 |
| 60 (Sensor Power Source) | At All Times | 4.8-5.2 |
| 66 (In-Car Temp. Sensor) | 77°C (25°C) (1) | 2.3-2.9 |
| 67 (Evaporator Thermistor) | 77°C (25°C) (1) (2) | 2.3-2.9 |
| (1) Sensor resistance should be 4000 ohms. (2) Measure voltage with A/C off. |
| (1) | Sensor resistance should be 4000 ohms. |
| (2) | Measure voltage with A/C off. |
IN-CAR TEMPERATURE SENSOR, AIR INLET TEMPERATURE SENSOR & EVAPORATOR THERMISTOR CIRCUIT TEST
COOLANT TEMPERATURE SENSOR & PHOTO SENSOR CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See COOLANT TEMPERATURE SENSOR & PHOTO SENSOR CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 59 (Coolant Temp. Sensor) | Ignition Off (1) | 12 |
| 59 (Coolant Temp. Sensor) | Ignition On (2) | 0 |
| 69 (Photo Sensor -) | In Sunlight (3) | 0.1 To -0.2 |
| 69 (Photo Sensor -) | In Darkness (4) | 0 |
| 70 (Photo Sensor +) | At All Times | 0 |
| (1) With coolant temperature less than 122°F (50°C). (2) With coolant temperature greater than 122°F (50°C). (3) Brightness at 100,000 lux or more. (4) Brightness at less than 0 lux. |
| (1) | With coolant temperature less than 122°F (50°C). |
| (2) | With coolant temperature greater than 122°F (50°C). |
| (3) | Brightness at 100,000 lux or more. |
| (4) | Brightness at less than 0 lux. |
COOLANT TEMPERATURE SENSOR & PHOTO SENSOR CIRCUIT TEST
BELT LOCK CONTROLLER CIRCUIT TEST
With A/C compressor operating, check voltage between ground and A/C control unit terminal No. 116 (A/C output signal). (Scheme 1) Voltage should be 10-12 volts. Belt lock controller is located under glove box.
BLEND-AIR SELECTOR, MODE SELECTOR & FRESH/RECIRCULATED AIR SELECTOR DAMPER MOTOR CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See BLEND-AIR DAMPER, MODE SELECTOR DAMPER & FRESH/RECIRCULATED AIR SELECTOR DAMPER MOTOR CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 102 (Fresh/Recirculated Air Selector Damper Motor -) | Recirc. Air Setting (1) | 0.5 |
| 102 (Fresh/Recirculated Air Selector Damper Motor -) | Fresh Air Setting (2) | 10 |
| 103 (Mode Selector Motor -) | Face Setting (3) | 0.5 |
| 103 (Mode Selector Motor -) | Defrost Setting (4) | 10 |
| 104 (Fresh/Recirculated Air Selector Damper Motor +) | Recirc. Air Setting (5) | 10 |
| 104 (Fresh/Recirculated Air Selector Damper Motor +) | Fresh Air Setting (6) | 0.5 |
| 105 (Blend-Air Motor +) | 63°F (17°C) (7) | 0.5 |
| 105 (Blend-Air Motor +) | 90.5°F (32.5°C) (8) | 10 |
| 111 (Blend-Air Motor -) | 63°F (17°C) (7) | 10 |
| 111 (Blend-Air Motor -) | 90.5°F (32.5°C) (8) | 0.5 |
| 112 (Mode Selector Motor +) | Face Setting (3) | 10 |
| 112 (Mode Selector Motor +) | Defrost Setting (4) | 0.5 |
| (1) Output turns off 40 seconds after damper moves to recirculated air setting. (2) Output turns off 40 seconds after damper moves to fresh air setting. (3) Output turns off 40 seconds after damper moves to face setting. (4) Output turns off 40 seconds after damper moves to defrost setting. (5) Output turns off 40 seconds after recirculated air has been activated. (6) Output turns off 40 seconds after fresh air has been activated. (7) Output turns off 40 seconds after damper moves to maximum cool setting. (8) Output turns off 40 seconds after damper moves to maximum hot setting. |
| (1) | Output turns off 40 seconds after damper moves to recirculated air setting. |
| (2) | Output turns off 40 seconds after damper moves to fresh air setting. |
| (3) | Output turns off 40 seconds after damper moves to face setting. |
| (4) | Output turns off 40 seconds after damper moves to defrost setting. |
| (5) | Output turns off 40 seconds after recirculated air has been activated. |
| (6) | Output turns off 40 seconds after fresh air has been activated. |
| (7) | Output turns off 40 seconds after damper moves to maximum cool setting. |
| (8) | Output turns off 40 seconds after damper moves to maximum hot setting. |
BLEND-AIR SELECTOR, MODE SELECTOR & FRESH/RECIRCULATED AIR SELECTOR DAMPER MOTOR CIRCUIT TEST
POWER TRANSISTOR & BLOWER MOTOR RELAY CIRCUIT TEST
Check voltage between ground and indicated A/C control unit terminals. See POWER TRANSISTOR & BLOWER MOTOR RELAY CIRCUIT TEST table. (Scheme 1)
| Terminal No. (Component/Circuit) | Condition | Volts |
|---|
| 51 (Power Transistor Collector) | OFF | 12 |
| 51 (Power Transistor Collector) | Low | 7 |
| 51 (Power Transistor Collector) | High | 0 |
| 52 (Power Transistor Base) | OFF | 0 |
| 52 (Power Transistor Base) | Low | Approx. 1.3 |
| 52 (Power Transistor Base) | High | Approx. 1.2 |
| 101 (High-Speed Relay) | High | 1.5 Or Less |
| 101 (High-Speed Relay) | Medium | 12 |
| 101 (High-Speed Relay) | Low | 12 |
| 101 (High-Speed Relay) | OFF | 12 |
POWER TRANSISTOR & BLOWER MOTOR RELAY CIRCUIT TEST
