Honda Civic. Manual — part 740

Fig. 31: Measuring Resistance Between No 3 And No 4 Terminals Of
Power Transistor
Courtesy of AMERICAN HONDA MOTOR CO., INC.

4. Carefully release the lock tab on the No. 1 terminal (YEL) (A) in the 4P

connector, then remove the terminal and insulate it from body ground.

Fig. 32: Identifying 4P Connector Terminal No. 1
Courtesy of AMERICAN HONDA MOTOR CO., INC.

5. Reconnect the 4P connector to the power transistor.
6. Make sure the YEL wire is completely isolated, then supply 12 V to the No. 1

cavity with a jumper wire.

7. Turn the ignition switch ON (II), and check that the blower motor runs.

If the blower motor does not run, replace the power transistor.

If the blower motor runs, the power transistor is OK.

2008 Honda Civic EX

2006-08 HVAC Heating - Civic (All Except Hybrid)

AIR MIX CONTROL MOTOR TEST

1. Disconnect the 7P connector from the air mix control motor.

2. Connect battery power to the No. 1 terminal of the air mix control motor, and

ground the No. 2 terminal; the air mix control motor should run, and stop at
Max Hot. If it doesn't, reverse the connections; the air mix control motor
should run, and stop at Max Cool. When the air mix control motor stops
running, disconnect battery power immediately.

Fig. 33: Identifying Air Mix Control Motor Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.

3. If the air mix control motor did not run in step 2, remove it, then check the air

mix control linkage and door for smooth movement.

If the linkage and door move smoothly, replace the air mix control motor
(see AIR MIX CONTROL MOTOR TEST ).

If the linkage or door sticks or binds, repair them as needed.

If the air mix control motor runs smoothly, go to step 4.

4. Measure the resistance between the No. 5 and No. 7 terminals. It should be

between 4.2 to 7.8 kohms.

5. Reconnect the air mix control motor 7P connector, then turn the ignition switch

NOTE:

Before testing, check for HVAC DTCs (see HOW TO USE
THE SELF-DIAGNOSTIC FUNCTION ).

NOTE:

Incorrectly applying power and ground to the air mix
control motor will damage it. Follow the instructions
carefully.

2008 Honda Civic EX

2006-08 HVAC Heating - Civic (All Except Hybrid)

ON (II).

6. Using the backprobe set. Measure the voltage between the No. 3 and No. 7

terminals.

Max Cool: about 0.5 V

Max Hot: about 4.5 V

7. If either the resistance or voltage readings are not as specified, replace the air

mix control motor (see AIR MIX CONTROL MOTOR TEST ).

AIR MIX CONTROL MOTOR REPLACEMENT

1. Remove the driver's dashboard undercover (see DRIVER's DASHBOARD

UNDERCOVER REMOVAL/INSTALLATION ).

2. Disconnect the 7P connector (A) from the air mix control motor (B). Remove

the self-tapping screws and the air mix control motor from the heater unit.

Fig. 34: Identifying 7P Connector And Air Mix Control Motor
Courtesy of AMERICAN HONDA MOTOR CO., INC.

3. Install the motor in the reverse order of removal. Make sure the pin on the

motor is properly engaged with the linkage. After installation, make sure the
motor runs smoothly.

MODE CONTROL MOTOR TEST

NOTE:

Before testing, check for HVAC DTCs (see HOW TO USE

2008 Honda Civic EX

2006-08 HVAC Heating - Civic (All Except Hybrid)

1. Disconnect the 7P connector from the mode control motor.

2. Connect battery power to the No. 1 terminal of the mode control motor, and

ground the No. 2 terminal; the mode control motor should run smoothly, and
stop at Vent. If it doesn't, reverse the connections; the mode control motor
should run smoothly, and stop at Defrost. When the mode control motor stops
running, disconnect battery power immediately.

Fig. 35: Identifying Mode Control Motor Terminals
Courtesy of AMERICAN HONDA MOTOR CO., INC.

3. If the mode control motor did not run in step 2, remove it, then check the mode

control linkage and doors for smooth movement.

If the linkage and doors move smoothly, replace the mode control motor
(see MODE CONTROL MOTOR TEST ).

If the linkage or doors stick or bind, repair them as needed.

If the mode control motor runs smoothly, go to step 4.

4. Use a digital multimeter with an output of 1 mA or less at the 20 k ohms range.

With the mode control motor running as in step 2, check for continuity
between the No. 3, 4, 5, and 6 terminals and the No. 7 terminal individually.
There should be continuity for a moment at each terminal as the motor moves
past the switch's terminal.

THE SELF-DIAGNOSTIC FUNCTION ).

NOTE:

Incorrectly applying power and ground to the mode
control motor will damage it. Follow the instructions
carefully.

2008 Honda Civic EX

2006-08 HVAC Heating - Civic (All Except Hybrid)