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A/C AMPLIFIER INSPECTION [FULL-AUTO AIR CONDITIONER]

BHE074061190W03

1. Turn the ignition switch to the ON position.

2. Connect the negative (-) lead of the tester to body ground.

3. By inserting the positive (+) lead of the tester into each A/C amplifier terminal, measure the voltage according to the terminal voltage table.

  • If there is any malfunction, inspect the parts under "Inspection item(s)".

  – If the parts under "Inspection item(s)" are found to be normal (except for terminal 1A), replace the A/C amplifier.
  – For terminal 1A, first try replacing the power transistor. If there is still any malfunction, replace the A/C amplifier.

## Terminal Voltage Table (Reference)

Terminal | Signal name | Connected to | Measurement condition | Voltage (V) | Inspection item(s)
--- | --- | --- | --- | --- | ---
1A | Blower fan speed control | Power transistor | Fan stopped | 1.0 or less | • A/C amplifier: terminal voltage (1A)
Fan: manual LO | 2.1
Fan: manual HI | 2.9
1B | Blower motor feedback | • Blower motor • Power transistor | Fan stopped | B+ | 1. Wiring harness: continuity, short circuit (A/C amplifier-power transistor: 1A-D, 1B-C) (Blower motor-blower relay: A-D) (Blower relay-fuse: C-HEATER 40 A, A-A/C 7.5 A) 2. Wiring harness: continuity (Power transistor-body ground: A-GND) (Blower relay-A/C amplifier: E-1L) 3. Power transistor 4. Blower motor 5. Blower relay 6. A/C 7.5 A fuse 7. HEATER 40 A fuse 8. Power transistor replacement
Fan: manual LO | 9.0
Fan: manual HI | 0.7
1C | Version signal (U.K. specs.) | Body ground | Under any condition | 1.0 or less | • Wiring harness: continuity (A/C amplifier-GND: 1C-GND)
1D | Version signal (European (L.H.D.) specs.) | Body ground | Under any condition | 1.0 or less | • Wiring harness: continuity (A/C amplifier-GND: 1D-GND)
1E | - | - | - | - | -
1F | - | - | - | - | -
1G | - | - | - | - | -
1H | - | - | - | - | -
1I | Motor operation | Air intake actuator | Switched to RECIRCULATE | 1.0 or less | • Wiring harness: continuity, short circuit (A/C amplifier-air intake actuator: 1I-A, 1J-C) • Air intake actuator
Switched to FRESH | 12
1J | Motor operation | Air intake actuator | Switched to RECIRCULATE | 12 | • Wiring harness: continuity, short circuit (A/C amplifier-air intake actuator: 1J-C, 1I-A) • Air intake actuator
Switched to FRESH | 1.0 or less
1K | Rear window defroster operation | Rear window defroster relay | Rear window defroster switch OFF | B+ | • Wiring harness: continuity, short circuit (A/C amplifier-rear window defroster relay: 1K-E) • Rear window defroster relay
Rear window defroster switch ON | 1.0 or less | • A/C amplifier: terminal voltage (2C, 2N)
1L | Blower motor operation | Blower relay | Fan switch OFF | B+ | • Wiring harness: continuity, short circuit (A/C amplifier-blower relay: 1L-E) • Blower relay
Fan switch ON | 1.0 or less | • A/C amplifier: terminal voltage (2C, 2N)
1M | A/C | Refrigerant pressure switch | Fan stopped | B+ | • Wiring harness: continuity, short circuit (A/C amplifier-refrigerant pressure switch: 1M-B) (Refrigerant pressure switch-PCM: C-4W) • Refrigerant pressure switch • PCM: terminal voltage (4W)
Fan switch: ON and A/C switch: ON | 1.0 or less | • A/C amplifier: terminal voltage (2C, 2N)
1N | - | - | - | - | -
1O | - | - | - | - | -
1P | Signal | - | - | - | -
1Q | - | - | - | - | -
1R | Signal | - | - | - | -
1S | - | - | - | - | -
1T | - | - | - | - | -
1U | Motor operation | Air mix actuator | Moving towards COLD | 1.0 or less | • Wiring harness: continuity, short circuit (A/C amplifier-air mix actuator: 1U-F (L.H.D.) G (R.H.D.), 1V-G (L.H.D.) F (R.H.D.)) • Air mix actuator
Moving towards HOT | 12
1V | Motor operation | Air mix actuator | Moving towards COLD | 12 | • Wiring harness: continuity, short circuit (A/C amplifier-air mix actuator: 1U-F (L.H.D.) G (R.H.D.), 1V-G (L.H.D.) F (R.H.D.)) • Air mix actuator
Moving towards HOT | 1.0 or less
1W | Motor operation | Airflow mode actuator | Switched to DEFROSTER | 12 | • Wiring harness: continuity, short circuit (A/C amplifier-airflow mode actuator: 1W-G, 1X-F) • Airflow mode actuator
Switched to VENT | 1.0 or less
1X | Motor operation | Airflow mode actuator | Switched to DEFROSTER | 1.0 or less | • Wiring harness: continuity, short circuit (A/C amplifier-airflow mode actuator: 1W-G, 1X-F) • Airflow mode actuator
Switched to VENT | 12
2A | B+ | ROOM 15 A fuse | Under any condition | B+ | • Wiring harness: continuity, short circuit (A/C amplifier- fuse: 2F-ROOM 15 A) • ROOM 15 A fuse
2B | - | - | - | - | -
2C | IG2 | A/C 7.5 A fuse | IG SW ON | B+ | • Wiring harness: continuity, short circuit (A/C amplifier- fuse: 2C-A/C 7.5 A) • A/C 7.5 A fuse
IG SW LOCK | 1.0 or less | • Wiring harness: continuity, short circuit (A/C amplifier- fuse: 2C-A/C 7.5 A)
2D | - | - | - | - | -
2E | - | - | - | - | -
2F | - | - | - | - | -
2G | Potentiometer input | Airflow mode actuator | VENT | 4.0 | • Wiring harness: continuity, short circuit (A/C amplifier-airflow mode actuator: 2G-E, 2P-C) • Airflow mode actuator • A/C amplifier: terminal voltage (2O)
BILEVEL | 3.3
HEAT | 2.6
HEAT/DEF | 1.8
DEFROSTER | 1.0
2H | Potentiometer input | Air mix actuator | Set temperature at MAX COLD | 3.9 | • Wiring harness: continuity, short circuit (A/C amplifier-air mix actuator: 2H-E, 2P-A (L.H.D.) C (R.H.D.)) • Air mix actuator • A/C amplifier: terminal voltage (2O)
Set temperature at MAX HOT | 1.1
2I | Solar radiation sensor input | Solar radiation sensor | Incandescent light (approx. 60 W) shined directly on the solar radiation sensor from a distance of approx. 100 mm {3.9 in} | 4.0 | • Wiring harness: continuity (A/C amplifier-solar radiation sensor: 2I-B, 2O-A) • A/C amplifier: terminal voltage (2O) • Solar radiation sensor
Blocking light to solar radiation sensor | 1.0 or less
2J | Evaporator temperature sensor input | Evaporator temperature sensor | Compared with temperature detected by evaporator temperature sensor | Refer to graph 1 | • Wiring harness: continuity (A/C amplifier-evaporator temperature sensor: 2J-B, 2P-A) • Wiring harness: short circuit (A/C amplifier-evaporator temperature sensor: 2J-B) • Evaporator temperature sensor • A/C amplifier: terminal voltage (2C, 2N)
2K | Ambient temperature sensor input | Ambient temperature sensor | Compared with temperature detected by ambient temperature sensor | Refer to graph 2 | • Wiring harness: continuity (A/C amplifier-ambient temperature sensor: 2K-B, 2P-A) • Wiring harness: short circuit (A/C amplifier-ambient temperature sensor: 2K-B) • Ambient temperature sensor • A/C amplifier: terminal voltage (2C, 2N)
2 L | Cabin temperature sensor input | Cabin temperature sensor | Compared with temperature detected by cabin temperature sensor | Refer to graph 3 | • Wiring harness: continuity (A/C amplifier-cabin temperature sensor: 2L-B, 2P-A) • Wiring harness: short circuit (A/C amplifier-cabin temperature sensor: 2L-B) • Cabin temperature sensor • A/C amplifier: terminal voltage (2C, 2N)
2M | ECT sensor input | PCM | Compared with temperature detected by ECT sensor | Refer to graph 4 | • Wiring harness: continuity, short circuit (A/C amplifier-PCM: 2M-5W) • ECT sensor • A/C amplifier: terminal voltage (2C, 2N)
2N | GND | Body ground | Under any condition | 1.0 or less | • Wiring harness: continuity (A/C amplifier-GND: 2N-GND)
2O | +5 V | • Air mix actuator • Airflow mode actuator • Solar radiation sensor | IG SW ON | 5.0 | • Wiring harness: short circuit (A/C amplifier-air mix actuator, airflow mode actuator, solar radiation sensor: 2O-C (L.H.D.) A (R.H.D.), A, A) • Air mix actuator • Airflow mode actuator • Solar radiation sensor • A/C amplifier: terminal voltage (2C, 2N)
IG SW LOCK | 1.0 or less | • A/C amplifier replacement
2P | Sensor GND | • Ambient temperature sensor • Cabin temperature sensor • Evaporator temperature sensor • Air mix actuator • Airflow mode actuator | Under any condition | 1.0 or less | • A/C amplifier: terminal voltage (2N)