Inspection Procedure 10

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:

CIRCUIT OPERATION
The A/C-ECU power system may be defective if the air conditioner, defogger, and outside/inside air selection damper motor all do not operate normally.

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

Required Special Tools:
- MB991223: Test Harness Set

STEP 1. Measure the voltage at A/C-ECU connector C-06.




1. Disconnect A/C-ECU connector C-06 and measure the voltage at the harness side.
2. Ignition switch: ON




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 4.

NO: Go to Step 2.

STEP 2. Check A/C-ECU connector C-06 for damage.




Q: Is A/C-ECU connector C-06 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. Check the wiring harness between A/C-ECU connector C-06 (terminal 10) and the ignition switch (IG2).

NOTE: Also check junction block connectors C-205 and C-203. If junction block connectors C-205 or C-203 is damaged, repair or replace the connector as described in Harness Connector Inspection.




Q: Is the wiring harness between A/C-ECU connector C-06 (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 4. Measure the resistance at A/C-ECU connector C-06 in order to check the ground circuit to the A/C-ECU.




1. Disconnect A/C-ECU connector C-06, 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 5.

STEP 5. Check A/C-ECU connector C-06 for damage.




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

YES: Go to Step 6.

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

STEP 6. Check the wiring harness between A/C-ECU connector C-06 (terminal 12) and the ground.




Q: Is the wiring harness between A/C-ECU connector C-06 (terminal 12) and the ground in good condition?

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

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