Alan_uk
A2OC Donor
This is a guide to repairing the Brake Sensor cable using a short repair cable. I obtained a VW short cable which much cheaper that the Audi long repair cable.
Problem
The brake pair wear symbol is displayed on the dash board.
Note: the sensor is only on the near-side front brake pad. There is an electrical circuit through a wire in the pads. When the pads wear the wire is broken (open circuit) and the brake pad wear symbol is displayed. The symbol will also be displayed if there is a break in the wiring (cabling). A circuit diagram and diagnostic guide for an A3 can be found here:
http://www.vwaudiforum.co.uk/forum/showthread.php?68730-should-my-car-have-brake-pads-wear-indicator The A2 might be similar but diagnostic guide is probably the same.
Possible Reasons for the Fault
1. The brake pads are indeed worn – replace.
2. The wire from the pads to the plug/socket situated on the front suspension is broken – buy new pads.
3. The plug/socket is broken – if the socket is broken then buy new pads. If the plug is broken then either buy a sensor wire repair kit or repair as per my other guide.
4. The wire from the plug/socket to the dash board is broken – if it is broken between the plug/socket and the main wiring harness then buy a sensor wire repair kit or possibly repair the wire yourself. If broken in the main wiring harness then a new wire will need to be run to the dashboard. There are 2 repair kits: short and long
This guide is for 4 using the short cable.
long repair cable, which is for both the brake sensor and ABS, is threaded into the engine compartment and then through the bulk head and down to the bottom of the A pillar by the passenger door where the connectors are. This is a difficult job. Alternatively some people have cut this long cable and spliced it into the loom inside the engine compartment.
short repair cable splices into the loom inside the wheel arch and keeps the existing ABS wires.
Disclaimer
This guide is used entirely at your own risk. The author is not responsible for any consequences in following this guide. This guide is definitely not recommended for fixing the ABS wheel rotation sensor.
Safety
As you will be working under the wheel arch without the wheel on, then support the car with axle stands. I slid a car ramp underneath the suspension with a block of hardwood on top. He then lower the vehicle until the ramp begins to take the weight.
New Short Cable and Circuit Diagram
The next photo shows the circuit diagram and the short cable. The circuit diagram was used to identify the brake sensor wires colours: Yellow and Red. Note that I've seen comments that Audi is not always consistent in the actual colours used.
Trial Fit to see where to join
I attached the socket to prongs on the hub and noted the position to splice.
Heat Shrink Butt Connectors
On the workbench I terminated the repair cable with butt terminators that are pre-covered in shrink wrap. I special tool is needed to squeeze the butt terminators. These terminators are preferred to soldering as solder joints can crack. Note that I offset the 2 terminators to reduce the overall thickness.
The tool may not be the correct one as the shrink wrap was not looking brilliant. It's imported that the wire is gently tugged to test it has been crimped. It's best to test crimping and the tool on some spare cable first. Sometimes using a too small an opening on the tool ends up with the butt terminator jammed in the claws.
continues ....................
Problem
The brake pair wear symbol is displayed on the dash board.
Note: the sensor is only on the near-side front brake pad. There is an electrical circuit through a wire in the pads. When the pads wear the wire is broken (open circuit) and the brake pad wear symbol is displayed. The symbol will also be displayed if there is a break in the wiring (cabling). A circuit diagram and diagnostic guide for an A3 can be found here:
http://www.vwaudiforum.co.uk/forum/showthread.php?68730-should-my-car-have-brake-pads-wear-indicator The A2 might be similar but diagnostic guide is probably the same.
Possible Reasons for the Fault
1. The brake pads are indeed worn – replace.
2. The wire from the pads to the plug/socket situated on the front suspension is broken – buy new pads.
3. The plug/socket is broken – if the socket is broken then buy new pads. If the plug is broken then either buy a sensor wire repair kit or repair as per my other guide.
4. The wire from the plug/socket to the dash board is broken – if it is broken between the plug/socket and the main wiring harness then buy a sensor wire repair kit or possibly repair the wire yourself. If broken in the main wiring harness then a new wire will need to be run to the dashboard. There are 2 repair kits: short and long
This guide is for 4 using the short cable.
long repair cable, which is for both the brake sensor and ABS, is threaded into the engine compartment and then through the bulk head and down to the bottom of the A pillar by the passenger door where the connectors are. This is a difficult job. Alternatively some people have cut this long cable and spliced it into the loom inside the engine compartment.
short repair cable splices into the loom inside the wheel arch and keeps the existing ABS wires.
Disclaimer
This guide is used entirely at your own risk. The author is not responsible for any consequences in following this guide. This guide is definitely not recommended for fixing the ABS wheel rotation sensor.
Safety
As you will be working under the wheel arch without the wheel on, then support the car with axle stands. I slid a car ramp underneath the suspension with a block of hardwood on top. He then lower the vehicle until the ramp begins to take the weight.
New Short Cable and Circuit Diagram
The next photo shows the circuit diagram and the short cable. The circuit diagram was used to identify the brake sensor wires colours: Yellow and Red. Note that I've seen comments that Audi is not always consistent in the actual colours used.
Trial Fit to see where to join
I attached the socket to prongs on the hub and noted the position to splice.
Heat Shrink Butt Connectors
On the workbench I terminated the repair cable with butt terminators that are pre-covered in shrink wrap. I special tool is needed to squeeze the butt terminators. These terminators are preferred to soldering as solder joints can crack. Note that I offset the 2 terminators to reduce the overall thickness.
The tool may not be the correct one as the shrink wrap was not looking brilliant. It's imported that the wire is gently tugged to test it has been crimped. It's best to test crimping and the tool on some spare cable first. Sometimes using a too small an opening on the tool ends up with the butt terminator jammed in the claws.
continues ....................
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