NO.7 AMOUNT OF AIR FROM REAR VENTS DOES NOT CHANGE

id070300901500

7
Amount of air from rear vents does not change
DESCRIPTION
•  Malfunction in rear blower motor system
•  Amount of air blowing rear vents does not change when switching front and/or rear climate control unit airflow volume control dial.
POSSIBLE CAUSE
•  Rear A/C unit malfunction
•  Rear blower motor malfunction
•  Rear power MOS FET malfunction
•  Rear climate control unit malfunction

•  When performing an asterisked (*) troubleshooting inspection, shake the wiring harness and connectors while doing the inspection to discover whether poor contact points are the cause of any intermittent malfunctions. If there is a problem, inspect to make sure connectors, terminals and wiring harness are connected correctly and undamaged.

Diagnostic procedure

STEP

INSPECTION

ACTION
1
INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR A/C UNIT OR ELSEWHERE
•  Turn the ignition switch to the ON position.
•  Turn the rear fan switch the ON position.
•  Does the blower motor rotate smoothly?
Yes
Go to the next step.
No
Go to Step 3.
2
INSPECT REAR A/C UNIT INTAKE VENT
•  Is the rear A/C unit intake vent clogged?
Yes
Remove obstruction, then go to Step 13.
No
Inspect if there are any obstructions in the rear A/C unit passage, then go to Step 13.
3*
INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR BLOWER RELAY SYSTEM OR REAR POWER MOS FET
•  Turn the ignition switch to ON position.
•  Turn the rear fan switch to OFF position.
•  Measure the voltage at the following rear blower motor terminal.
―  Terminal B (rear blower motor operation signal)
•  Is the voltage normal (B+)?
Yes
Go to the Step 7.
No
Go to the next step.
4*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN OR SHORT CIRCUIT BETWEEN FUSE BLOCK AND REAR BLOWER RELAY) OR ELSEWHERE
•  Measure the voltage at the following rear relay terminals.
―  Terminal A (IG2 signal)
―  Terminal D (B+ signal)
•  Is the voltage approx. 12 V?
Yes
Go to the next step.
No
If the terminal A voltage is not normal, repair or replace wiring harness between A/C 7.5 A fuse and rear blower relay.
If the terminal D voltage is not normal, repair or replace wiring harness between R.HEATER 40 A fuse and rear blower relay.
Then go to Step 13.
5*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN CIRCIT BETWEEN REAR BLOWER RELAY AND GROUND) OR ELSEWHERE
•  Measure the voltage at the following rear blower relay terminal.
―  Terminal B (GND signal)
•  Is the voltage approx. 0 V?
Yes
Go to the next step.
No
Repair or replace for open circuit between rear blower relay and GND, then go to Step 13.
6*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN OR SHORT CIRCUIT BETWEEN REAR BLOWER RELAY AND REAR BLOWER MOTOR) OR ELSEWHERE
•  Measure the voltage at the following rear blower relay terminal.
―  Terminal B (blower motor operation signal)
•  Is the voltage approx. 12 V?
Yes
Repair or replace for open or short circuit between rear blower relay and rear blower motor, then go to Step 13.
No
Replace the rear blower relay, then go to Step 13.
7*
INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR BLOWER MOTOR OR ELSEWHERE
•  Measure the voltage at the following rear blower motor terminal.
―  Terminal A (blower motor operation signal)
•  Is the voltage approx. 12 V?
Yes
Go to the next step.
No
Replace the rear blower motor, then go to Step 13.
8*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN OR SHORT CIRCUIT BETWEEN REAR BLOWER MOTOR AND REAR POWER MOS FET) OR ELSEWHERE
•  Measure the voltage at the following rear power MOS FET terminal.
―  Terminal B (blower motor operation signal)
•  Is the voltage approx. 12 V?
Yes
Go to the next step.
No
Repair or replace for open or short circuit between rear blower motor and rear power MOS FET, then go to Step 13.
9*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN CIRCUIT BETWEEN REAR POWER MOS FET AND GROUND) OR ELSEWHERE
•  Is there continuity at the following terminals?
―  Terminal (wiring harness-side connector) A—GND
Yes
Go to the next step.
No
Repair or replace for open circuit between rear power MOS FET and GND, then go to Step 13.
10
INSPECT REAR A/C UNIT
•  Inspect the fan in rear A/C unit.
―  Is the fan free of interference with the rear A/C unit case?
―  Is the fan free of foreign material and obstructions?
•  Is the fan normal?
Yes
Go to the next step.
No
Remove obstruction, repair or replace the fan blower unit case, then go to Step 13.
11*
INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (OPEN CIRCUIT BETWEEN REAR POWER MOS FET AND CLIMATE CONTROL UNIT) OR ELSEWHERE
•  Turn the ignition switch to LOCK position.
•  Disconnect the front climate control unit connector (24-pin).
•  Is there continuity following terminals at harness-side connector.
―  Terminal D (rear power MOS FET) and terminal 1R (front climate control unit)
―  Terminal C (rear power MOS FET) and terminal 1T (front climate control unit)
Yes
Replace the rear power MOS FET, then go to the next step.
No
Repair or replace for open circuit between the rear power MOS FET and the front climate control unit, then go to Step 13.
12
INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR POWER MOS FET OR ELSEWHERE
•  Is the air discharged from rear vent after replace the rear power MOS FET?
Yes
Troubleshooting completed.
Explain repairs to customer.
No
Replace the front climate control unit, then go to the next step.
13
VERIFY REPAIR
•  Is the air discharged from rear vent?
Yes
Troubleshooting completed.
Explain repairs to customer.
No
Recheck malfunction symptoms, then repeat from Step 1 if the malfunction recurs.