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Golf Mk5: Fuse 4 keeps blowing – A/C, reverse lights and rear parking sensors not working
I am posting this because the fault can look like several unrelated component failures, when the actual cause may be damaged wiring at the bonnet hinge.
Vehicle covered:
On cars with heated windscreen washer jets, the wiring loom runs through the bonnet-hinge area and flexes every time the bonnet is opened or closed. With age, tight routing or a previous repair, the insulation and conductor strands can become damaged.
If one of these wires shorts, fuse SC4 opens and several systems lose their shared power supply. This is why the car can show A/C, reverse-light and oil-temperature faults at the same time.
The rear parking sensors may also stop working because the reversing-lamp or reverse-recognition signal has been lost. This does not automatically mean that a parking sensor or the parking-aid control unit is faulty.
Photo of the fault area:
Diagnosis and repair:
The exact fuse assignment depends on the vehicle’s production date and equipment. Always confirm it using the VIN-specific fuse chart and current-flow diagram.
Depending on the vehicle, SC4 may supply:
Do not replace G65, J255, G266 or parking-aid components only because a related fault code is stored. Check the shared power supply, fuse and bonnet-hinge wiring first.
Optional printable version
Just a quick disclaimer: this is based on what I found and repaired on the car, and I’m sharing it in case it helps someone else. It isn’t an official Volkswagen or StaggeredSix service bulletin, so please double-check the fuse layout and wiring diagram for your exact car before doing any work.
I am posting this because the fault can look like several unrelated component failures, when the actual cause may be damaged wiring at the bonnet hinge.
Vehicle covered:
- Volkswagen Golf Mk5 (1K)
- Model years: 2007–2009
- Mainly vehicles equipped with heated windscreen washer jets
- Air-conditioning or Climatronic does not work.
- Reversing lamp(s) do not work.
- Rear parking aid / rear parking sensors do not operate when reverse is selected.
- Fuse SC4 (fuse position 4 in the side-of-dashboard fuse carrier) blows repeatedly.
- The fuse may blow when the bonnet is opened, closed or moved.
- 00819 – High-pressure sensor (G65), electrical fault
- 01320 – Control module for Climatronic (J255), fault or no communication
- P0196 – Engine oil temperature sensor circuit, range/performance
- B10AE12 – High-pressure sensor, short to positive (wording can vary depending on the scan tool)
On cars with heated windscreen washer jets, the wiring loom runs through the bonnet-hinge area and flexes every time the bonnet is opened or closed. With age, tight routing or a previous repair, the insulation and conductor strands can become damaged.
If one of these wires shorts, fuse SC4 opens and several systems lose their shared power supply. This is why the car can show A/C, reverse-light and oil-temperature faults at the same time.
The rear parking sensors may also stop working because the reversing-lamp or reverse-recognition signal has been lost. This does not automatically mean that a parking sensor or the parking-aid control unit is faulty.
Photo of the fault area:
Diagnosis and repair:
- Confirm that SC4 is blown and check the correct fuse rating for the exact vehicle. Do not fit a higher-rated fuse.
- Save a complete vehicle scan before disturbing the wiring.
- Switch off the ignition, remove the key and follow the correct workshop procedure for disconnecting the battery.
- Inspect the loom at the left bonnet hinge, especially the branch for the heated washer jets. Remove only enough tape or conduit to expose the flexing section.
- Look for split insulation, exposed copper, broken strands, pinched wires and previous repairs.
- Use the correct current-flow diagram to test continuity and check for an unintended connection to ground or battery positive. Move the bonnet and flex the loom gently while testing.
- Repair damaged wires using automotive-grade cable of the same cross-section. Stagger and seal the splices, restore the conduit and leave enough free length for the full bonnet movement.
- Route and secure the loom away from sharp edges and hinge pinch points.
- Install the correct fuse, reconnect the battery, clear the fault codes and test the vehicle again.
- Air-conditioning or Climatronic operation
- Reversing lamps
- Rear parking aid / rear parking sensors
- Engine-oil temperature reading
- Heated washer-jet operation
- Full bonnet movement without the fuse blowing
- Final diagnostic scan with no returning faults
The exact fuse assignment depends on the vehicle’s production date and equipment. Always confirm it using the VIN-specific fuse chart and current-flow diagram.
Depending on the vehicle, SC4 may supply:
- G266 – Engine oil level / temperature sender
- M17 – Reversing lamp bulb
- J255 – Climatronic control unit
- G65 – High-pressure sensor
- E16 – Heater / heat-output switch
- J530 – Garage-door operation control unit
- G128 – Front passenger seat-occupancy sensor
- Y7 – Automatic anti-dazzle interior mirror
- E422 – Tyre-pressure monitor display button
- K216 – ESP warning lamp 2
- Z20 – Left heated washer-jet element
- Z21 – Right heated washer-jet element
Do not replace G65, J255, G266 or parking-aid components only because a related fault code is stored. Check the shared power supply, fuse and bonnet-hinge wiring first.
Optional printable version
Just a quick disclaimer: this is based on what I found and repaired on the car, and I’m sharing it in case it helps someone else. It isn’t an official Volkswagen or StaggeredSix service bulletin, so please double-check the fuse layout and wiring diagram for your exact car before doing any work.
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