Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSFORD2007FOCUS L4-2.3L VIN ZREPAIR AND DIAGNOSISWINDOWS AND GLASSWINDOWSTESTING AND INSPECTIONPINPOINT TESTSTEST I: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY
2007 Ford Focus L4-2.3L VIN Z
Test I: The Defrost System Will Not Shut Off Automatically
2007 Ford Focus L4-2.3L VIN ZSECTION Test I: The Defrost System Will Not Shut Off Automatically
PINPOINT TEST I: THE DEFROST SYSTEM WILL NOT SHUT OFF AUTOMATICALLY
Normal Operation
With the key in the START or RUN position and the rear window heater switch turned to the on position, the rear window defrost relay is energized providing voltage to the rear window defrost grid on circuit 15S-HB19 (GN/BU), the LH exterior rear view mirror on circuit 15S-HB35 (GN/BK) and the RH exterior rear view mirror on circuit 15S-HB36 (GN/OG). On 3-door and 5-door models, the rear window defrost grid is connected directly to ground. For all other models, the rear window defrost grid is connected to ground through circuit 31-HB19 (BK). The LH exterior rear view mirror is grounded through circuit 31-HB35 (BK). The RH exterior rear view mirror is grounded through circuit 31-HB36 (BK). Once the rear window heater switch is released, the generic electronic module (GEM) keeps the rear window defrost relay energized for a predetermined length of time by providing an alternative path to ground on circuit 31S-HB20 (BK/GN).
Possible Causes
- Circuit 15S-HB2 (GN/BU) short to voltage
- Circuit 15S-HB19 (GN/BU) short to voltage
- Circuit 31S-HB20 (BK/GN) short to ground
- Circuit 31S-HB31 (BK/OG) short to ground
- Rear window defrost relay
- Central junction box (CJB)
- GEM
- Heater control module
I1:
I1-I2:
I2-I3:
I3-I4:
I4-I6:
I6-I7:
Normal Operation
With the key in the START or RUN position and the rear window heater switch turned to the on position, the rear window defrost relay is energized providing voltage to the rear window defrost grid on circuit 15S-HB19 (GN/BU), the LH exterior rear view mirror on circuit 15S-HB35 (GN/BK) and the RH exterior rear view mirror on circuit 15S-HB36 (GN/OG). On 3-door and 5-door models, the rear window defrost grid is connected directly to ground. For all other models, the rear window defrost grid is connected to ground through circuit 31-HB19 (BK). The LH exterior rear view mirror is grounded through circuit 31-HB35 (BK). The RH exterior rear view mirror is grounded through circuit 31-HB36 (BK). Once the rear window heater switch is released, the generic electronic module (GEM) keeps the rear window defrost relay energized for a predetermined length of time by providing an alternative path to ground on circuit 31S-HB20 (BK/GN).
Possible Causes
- Circuit 15S-HB2 (GN/BU) short to voltage
- Circuit 15S-HB19 (GN/BU) short to voltage
- Circuit 31S-HB20 (BK/GN) short to ground
- Circuit 31S-HB31 (BK/OG) short to ground
- Rear window defrost relay
- Central junction box (CJB)
- GEM
- Heater control module
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.