Honda Civic. Manual — part 759

YES - Go to step 9.

NO - Go to step 25.

9. Turn the ignition switch to LOCK (0).

10. Disconnect the jumper wire.
11. Disconnect the power transistor 4P connector.
12. Check for continuity between the power transistor 4P connector terminal No. 2

and body ground.

Fig. 25: Checking Continuity Between Power Transistor 4P Connector
Terminal No. 2 And Body Ground

Is there continuity?

YES - Go to step 13.

NO - Check for an open in the wire between the power transistor and body
ground. If the wire is OK, check for poor ground at G401 (see CONNECTOR
TO HARNESS INDEX ).

13. Connect the power transistor 4P connector terminals No. 2 and No. 4 with a

jumper wire.

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

Fig. 26: Connecting Power Transistor 4P Connector Terminals No. 2 And
No. 4 With Jumper Wire

14. Turn the ignition switch ON (II).

Does the blower motor run at high speed?

YES - Go to step 15.

NO - Repair open in the GRN wire between the power transistor and the
blower motor.

15. Turn the ignition switch to LOCK (0).
16. Disconnect the jumper wire.
17. Disconnect the HVAC control unit 24P connector.
18. Check for continuity between body ground and the HVAC control unit 24P

connector terminals No. 7 and No. 8 individually.

Fig. 27: Checking Continuity Between Body Ground And HVAC Control
Unit 24P Connector Terminals No. 7 And No. 8

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

Is there continuity?

YES - Repair any short to body ground in the wires between the HVAC
control unit and the power transistor.

NO - Go to step 19.

19. Check for continuity between the following terminals of the HVAC control

unit 24P connector and the power transistor 4P connector.

HVAC CONTROL UNIT 24P CONNECTOR AND POWER
TRANSISTOR 4P CONNECTOR

Fig. 28: Checking Continuity Between HVAC Control Unit 24P And
Power Transistor 4P Connector Terminals

Is there continuity?

YES - Go to step 20.

NO - Repair any open in the wires between the HVAC control unit and the
power transistor.

20. Turn the ignition switch ON (II).

24P

4P

No. 7

No. 3

No. 8

No. 1

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)

21. Measure the voltage between body ground and the HVAC control unit 24P

connector terminals No. 7 and No. 8 individually.

Fig. 29: Measuring Voltage Between Body Ground And HVAC Control
Unit 24P Terminals No. 7 And No. 8

Is there voltage?

YES - Repair short to power in the wires.

NO - Go to step 22.

22. Turn the ignition switch to LOCK (0).
23. Reconnect the HVAC control unit 24P connector.
24. Test the power transistor (see POWER TRANSISTOR TEST ).

Is the power transistor OK?

YES - Check for loose wires or poor connections at the HVAC control unit
24P connector and at the power transistor 4P connector. If the connections are
good, substitute a known-good HVAC control unit, and recheck. If the
symptom/indication goes away, replace the original HVAC control unit.

NO - Replace the power transistor (see POWER TRANSISTOR TEST ).

25. Turn the ignition switch to LOCK (0).
26. Disconnect the jumper wire.
27. Disconnect the blower motor 2P connector.

2008 Honda Civic EX

2006-08 HVAC Heating/Air Conditioning - Civic (All Except Hybrid)