Inspection Procedure 10

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

DIAGNOSIS

Required Special Tool:
- 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. 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 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. 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 C-06 in good condition?

YES: Go to Step 6.

NO: Repair or replace the connector. 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.