Inspection of Auto A/C Panel and Its Circuit
Precautions: Precautions for Diagnosing Trouble · General safety (00)
Auto A/C panel and its circuits can be checked at auto A/C panel wiring connector by measuring voltage.
NOTICE:
If you connect a voltmeter or an ohmmeter directly to the auto A/C panel with the auto A/C panel connector disconnected, you can damage the auto A/C panel.
Never connect a voltmeter or an ohmmeter directly to any terminal on the auto A/C panel with the auto A/C panel connector disconnected.
Voltage and Signal Check
1)Remove auto A/C panel referring to Auto A/C Panel Removal and Installation:Automatic Type.
2)Connect “G227” connector.
3)Check voltage and signal at each terminal.
NOTE:
•As each terminal voltage is affected by the battery voltage, check that battery voltage is 11 V or more with ignition “ON”.
•Normal voltage of circuits with asterisk (*1) cannot be measured correctly with voltmeter because they are pulse signals. Check them with oscilloscope.
•Normal voltage of circuits with asterisk (*1) cannot be measured correctly with voltmeter because they are pulse signals. Check them with oscilloscope.
| [A]: | Auto A/C panel connector (View: [a]) | 1. | Auto A/C panel |
“G227” connector
| Terminal No. | Wire color | Circuit | Normal voltage | Condition |
|---|---|---|---|---|
| G227-1 | LT GRN | Power supply for backup | Approx. 12 V | Any condition |
| G227-2 | RED | Illumination switch | 0 V | Ignition: “ON” Lighting switch: OFF position |
| Approx. 12 V | Ignition: “ON” Lighting switch: ON position |
|||
| G227-4 | PPL | Ground for illumination | 0 V | Ignition: “ON” Lighting switch: OFF position |
| G227-5 | YEL | Power supply | Approx. 12 V | Ignition: “ON” |
| G227-7 | LT GRN | LIN communication signal *1 | Refer to Reference Waveform. | |
| G227-8 | GRY | Ground for auto A/C panel | 0 V | Ignition: “ON” |
Reference Waveform
Oscilloscope display
Shown below is typical waveform display provided by oscilloscope.
NOTE:
•Display includes the following types of data:
•Waveform varies depending on measurement condition and vehicle spec.
| [a]: | Waveform of channel 1 | [c]: | VOLT/DIV of each channel |
| [b]: | Ground level of each channel | [d]: | TIME/DIV |
LIN communication signal (1)
| Channel | Probe | Terminal No. |
|---|---|---|
| 1 | + | G227-7 |
| – | G227-8 |
| 1. | LIN communication signal |