Inspection Procedure 9

Malfunction of the A/C-ECU Power supply system.

A/C-ECU Power Supply Circuit Part 1:

A/C-ECU Power Supply Circuit Part 2:

TECHNICAL DESCRIPTION (COMMENT)
The A/C-ECU power system may be defective if the air conditioner, defogger, and outside/inside air changeover damper motor all do not operate normally.

TROUBLESHOOTING HINTS
- Malfunction of the A/C-ECU
- Damaged harness wires or connectors

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set




STEP 1. Check A/C-ECU connector C-05 for damage.

Q: Is A/C-ECU connector C-05 in good condition?

YES : Go to Step 2.

NO : Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning works normally.




STEP 2. Check A/C-ECU connector C-05 for damage.

Q: Is A/C-ECU connector C-05 in good condition?

YES : Go to Step 3.

NO : Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning works normally.

STEP 3. Measure the voltage at A/C-ECU connector C-05.




1. Disconnect A/C-ECU connector C-05 and measure the voltage at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal 10 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).

Q: Does the measured voltage correspond with this range?

YES : Go to Step 5.

NO : Go to Step 4.







STEP 4. Check the wiring harness between A/C-ECU connector C-05 (terminal 10) and the ignition switch (IG2).

NOTE: Also check junction block connectors C-212 and C-215.
If junction block connectors C-212 or C-215 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-05 (terminal 10) and the ignition switch (IG2) in good condition?

YES : Check that the air conditioning works normally.

NO : Repair the wiring harness. Check that the air conditioning works normally.

STEP 5. Measure the resistance at A/C-ECU connector C-05.




1. Disconnect A/C-ECU connector C-05, and measure at the wiring harness side.




2. Measure the resistance between terminal 12 and ground.
- The measured value should be 2 ohms or less.

Q: Does the measured resistance value correspond with this range?

YES : Replace the A/C-ECU, and check that the air conditioning works normally.

NO : Go to Step 6.







STEP 6. Check the wiring harness between A/C-ECU connector C-05 (terminal 12) and the ground.

NOTE: Also check joint connector (3) connectors C-10. If joint connector (3) connectors C-10 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between A/C-ECU connector C-05 (terminal 12) and the ground in good condition?

YES : Check that the air conditioning works normally.

NO : Repair the wiring harness. Check that the air conditioning works normally.