Inspection Procedure 9

Malfunction of the heater control Power Supply System.

Heater Control Power Supply Circuit Part 1:

Heater Control Power Supply Circuit Part 2:

TECHNICAL DESCRIPTION (COMMENT)
The heater control power system may be defective if the air conditioner, rear window defogger, and outside/inside air selection damper motor all do not operate normally.

TROUBLESHOOTING HINTS
- Malfunction of the heater control
- The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector

DIAGNOSIS

Required Special Tools:
- MB991223: Test Harness Set

STEP 1. Measure the voltage at heater control connector C-16.




1. Disconnect heater control connector C-16 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: Is the measured voltage approximately 12 volts?

YES: Go to Step 4.

NO: Go to Step 2.




STEP 2. Check heater control connector C-16 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is heater control connector C-16 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 heater control connector C-16 (terminal 10) and the ignition switch (IG2).

NOTE: Also check junction block connectors C-214 and C-211 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If junction block connectors C-214 and C-211 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between heater control connector C-16 (terminal 10) and the ignition switch (IG2) in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Cope with intermittent Malfunctions.

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

STEP 4. Measure the resistance at heater control connector C-16.




1. Disconnect heater control connector C-16, 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 heater control, and check that the air conditioning works normally.

NO: Go to Step 5.




STEP 5. Check heater control connector C-16 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Is heater control 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 heater control connector C-16 (terminal 12) and the ground.






NOTE: Also check joint connector 3. connectors C-06 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector 3. connectors C-06 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q: Is the wiring harness between heater control connector C-16 (terminal 12) and the ground in good condition?

YES: It can be assumed that this malfunction is intermittent. Refer to How to Cope with intermittent Malfunctions.

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