Brake Pad Wear Sensor Repair Guide - Repairing the Socket

This is a guide to repairing the brake wear sensor plug and socket.

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 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 (see photo 0)



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 this 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.

This guide covers situation 3.

Official solution for 3: The sensor wire repair kit is about £50. The kit has a Y cable for both the wheel rotation sensor and the break pad wear sensor. The cable is threaded through a hole in the wheel arch to the engine compartment. Here the old cable is cut and the new one soldered into the wiring harness.

continues

 

[Alan_uk]

part 2 - Authors situation

Author’s situation

The outer casing of the plug (harness side) of the plug/socket was broken. Judging by the dirt that had ingress into inside, it looked like it had been broken for some time. Eventually the wire had also broken and the alarm sounded.

See photos 1 to 3 showing the break (red arrow) and the locating bracket (blue arrow)

Cause is possibly

- jolt from hitting pothole
- brittle with age
- knocked and broken by clumsy mechanic



continues

 

[Alan_uk]

part 3 - Removing the Broken Plug

Removing the Broken Plug

First I had to disconnect the plug and socket. Spike has previous pointed to a photo showing how to leaver Audi connectors open but I still managed to break the clip.
See here: http://www.a2oc.net/forum/showthread.php?10752-Audi-Connectors-How-to-Release

As the plug was broken at the back I found that the pin could be pushed through and removed where the break was (or maybe it came out of the front of the plug – I can’t remember).

Photo 4 shows inside the plug with the missing pin. Photo 5 shows the pin. I noticed that there was a small gap inside the back of the pin (photo 6) and decided to solder 2 fine wires (fuse wire I think) into these gaps.




continues part 4

 

[Alan_uk]

part 4 - Repairing the Plug Pins

Repairing the Plug Pins

I cleaned the gaps with a pointed file and then tinned the fine wires with solder – a good 3cm needs tinning. I jammed the pin into a jig to hold it (photo 7) and then soldered in the wires to the pin and to themselves (photo 8). I needed 2 attempts as the wires did not strongly solder – it needed a bit more heat which melted the plastic casing a bit.

Next I shortened the fine wires so that they could fit into the back of the plug, ensuring all the remaining wire was tinned (photo 9).



continues part 5

 

[Alan_uk]

part 5 – Reconnecting the Plug Pins

Reconnecting the Plug Pins

I then cleaned the broken wire from the harness where it entered the plug and tinned it.

The next bit was a fiddle. I passed the pin back into the back end of the plug and held the front of the pin with long nose pliers inserted into the plug. I now had to bring the back end of the pin (with my extended wires) into contact with the wire from the harness. At the same time solder with fresh solder (photo 10).

This needs 4 hands! What I did was to unravelled some multi-core solder, place the reel at some point on the suspension with blue-tak and then and positioned the end of the multi-core solder next to the broken wire. More blue-tak holds the backend of the broken plug. A quick touch with the soldering iron on the solder and then straight onto the 2 wires to be joined.



continues part 6

 

[Alan_uk]

part 6 – Reassembling the Plug

Reassembling the Plug

Next job was to glue the broken plug together. I used Araldite fast setting epoxy resin. Before mixing I prepared some small pieces of plywood and g-clamps set at the right distance. Using a matchstick I pushed the resin into the backend of the plug and around the broken area. I took care not to have excessive resin on the sides of the groove around the plug otherwise the plug will not go back into the slot on the bracket.

I then clamped together (photo 11). This is a fiddle as the plywood does want to stay flat against the oval plug, but one needs to move fast as the resin starts going firm after a few minutes. Finally I position it so that the outside of the groove was facing up and then dropped a blob of resin on this side for extra strength (red arrow in photo 11). It will naturally spread out before setting.

As a final check I looked inside the plug to make sure the pin was straight – mine wasn’t so it made it straight with the long-nose pliers (photo 12).

I then switched on the ignition. The brake wear sensor warning light should come on (the brake pad cable has yet to be connected). It the warning light does not come on then there is a short circuit. The pins are probably touching at the ends or where the wire was soldered. You are now up against it to fix before the resin sets hard.



continues part 7

 

[Alan_uk]

part 7 – Reconnecting the Plug

Reconnecting the Plug

When the resin was set I reconnected the plug and socket and checked that the plug could slide back into the bracket (photo 13). I needed to trim a bit off with a knife (photo 14). Finally as I had broken the clip I sealed the plug and socket with tape to keep it joined together and the dirt and moisture out, though it is a tight fit (photo 15). I only had electrical tape to hand. It needs a waterproof fabric tape.

I then switched on the ignition again for a final check - the warning light should not come on.



The repair has been OK now for over a month.

- end -

 

[spartacus 68]

Nice repair thread.

Had a similar problem, but mine was with the wiring at the pad end. Stripped back the remaining plastic sheath and soldered the wiring. I then used fibreglass epoxy resin (sets in minutes) and is rock-hard. Better than Araldite in my opinion. Double-check connections before gluing - because once set it's on for good!

 

[mipayne]

I have just recently replaced the pads and one of the previous owners has cut the original connector off and replaced it with bullet connections. Do you have a part number for the original connector or the genuine replacement cable?

I was going to just cut the connector on the new pads, but really don't want to have to add another step when changing brake pads in the future.

Thanks for you help.

 

[Alan_uk]

Hi

Sorry don't have the part number but Skipton has access to Audi documentation. I'm sure he will be along soon

The replacement cable is a "repair" and actually needs to be spliced into the main wiring loom. From what I've read elsewhere that is usually done inside the engine compartment. I suppose you could use these cable connectors that you squeeze to cut into the cable but soldering is usually recommended. But given that an open connection triggers an alarm I personally would probably use those connectors (i.e. failure would give an alarm).

You could I suppose try to get a connector with a short length of cable attached of a old A2 then connect them with solder or a connector and then well seal the join to keep out water etc. Just an idea.

 

[Little Dog]

I've got this problem; probably a clumsy MOT tester combined with a brittle connector.

Is the female connector not available anywhere? £50 for a harness appears a bit excessive if the terminals can be released from the old connector and inserted into a new one.

Even if you have to buy the harness (very wasteful) the easiest fitting option would be to swop the new connector onto the old harness?

Is a brake wear indicator a mandatory requirement? I've never had one come on any car I have owned and A2 bake pads are so chunky that the disks wear out before the pads in my experience.

Great thread by the way; very informative thank you.

 

[Birchall]

I've got this problem; probably a clumsy MOT tester combined with a brittle connector.

Is the female connector not available anywhere? £50 for a harness appears a bit excessive if the terminals can be released from the old connector and inserted into a new one.

Even if you have to buy the harness (very wasteful) the easiest fitting option would be to swop the new connector onto the old harness?

Is a brake wear indicator a mandatory requirement? I've never had one come on any car I have owned and A2 bake pads are so chunky that the disks wear out before the pads in my experience.

Great thread by the way; very informative thank you.

There is a common problem on the A2 where the loom breaks just inside the engine compartment on the wheel tub. So these need the long harness to replace the broken cables.

It is an easy repair if the plugs are the only problem, just splice the wiring into the wires on the pads.

I think that you ill find that it is NOT an MOT failure, the reason being that if the warning was off or on, they heck the pad thickness. Even if the pads are worn sufficiently to trigger the warning light then they cannot fail the car because of this, they can only fail it if the thickness of the remaining pad material is below the allowed level.
So the warning light is to advise you to check the brake pads, it is not a reliable indicator as such.

Steve B

 

[Little Dog]

I don't have any broken cables (not yet anyway) its just the female connector on the hub that that has cracked. If I don't fix it then the wires will fatigue and break at this point.

I've been down to my local Audi dealer, told them about the problem, and suggested a new connector would be preferable to the harness. They agreed and went searching for a part number. They came back, after a little while, with a part number and a price less than £3. They are confident it is the correct part so I ordered one.

I'll post the part number once I have received it and if the part is correct.

Thanks Steve B, as a fall back it appears I could simply jump the wires on the car side and cut the wires off the pad? Then there would be no warning light showing in the car and I have a permanent fix. I will check though and, also, I'll try the replacement connector first.

Phil

 

[Little Dog]

There is a common problem on the A2 where the loom breaks just inside the engine compartment on the wheel tub. So these need the long harness to replace the broken cables.

It is an easy repair if the plugs are the only problem, just splice the wiring into the wires on the pads.

I think that you ill find that it is NOT an MOT failure, the reason being that if the warning was off or on, they heck the pad thickness. Even if the pads are worn sufficiently to trigger the warning light then they cannot fail the car because of this, they can only fail it if the thickness of the remaining pad material is below the allowed level.
So the warning light is to advise you to check the brake pads, it is not a reliable indicator as such.

Steve B

Steve

I initially missed your point / points, sorry. What is this issue with wiring breaking and where does it occur please?

Yes my problem is the connector; it has broken but I don't want to splice wires. So I will:

1. fit the connector I have bought, anybody know how to do this, it appears to have a complicated terminal retaining clip inside.

2. bypass the whole pad thickness circuit but first I need to check if this is allowed.

Sometimes features on cars are requirements of other markets. One of my cars wouldn't start unless the clutch was depressed; apparently a Canadian requirement? Anyway if the switch stuck the car wouldn't start. Solution, bin the switch and jump a wire across then two terminals the switch plugged on to. I'm feeling the same way about this pad thickness circuit.

 

[Birchall]

Steve

I initially missed your point / points, sorry. What is this issue with wiring breaking and where does it occur please?

Yes my problem is the connector; it has broken but I don't want to splice wires. So I will:

1. fit the connector I have bought, anybody know how to do this, it appears to have a complicated terminal retaining clip inside.

2. bypass the whole pad thickness circuit but first I need to check if this is allowed.

Sometimes features on cars are requirements of other markets. One of my cars wouldn't start unless the clutch was depressed; apparently a Canadian requirement? Anyway if the switch stuck the car wouldn't start. Solution, bin the switch and jump a wire across then two terminals the switch plugged on to. I'm feeling the same way about this pad thickness circuit.

Hi,

With the wire flexing so much over ten or more years, the very thin wires sometimes part company inside the loom.
This is often just where the wires go through the wheel tub into the engine bay (either side of this)

One cure is to break into the loom just past this (very carefully) and short out the two wires. That cancels the warning but you now have no low pad wear warning, so the ideal solution is to buy the repair loom from an Audi dealer and do a neat and permanent fix to keep everything functioning.
So if anyone finds that their pad wear warning light is on all the time, even when you short out the plug at the pads, then you have a break in the loom.
If shorting them out solves the problem then the connection in the pads or the plug itself is dodgy.

But in your case you seem to just have the problem with the plug which is a cheap repair.

Coincidentally, today I had to bypass the sensor on my wife's A2 because the sensor wires in the brand new (high quality) brake pads came out of the pad and the warning was on all the time. No real fix for this because the break was inside the pads and it was not worth buying more new and expensive pads just to fix that.

As we VERY regularly service, maintain and inspect our A2s it is not a problem to have the pads physically inspected often.

Steve B

 

[Little Dog]

A2 fixed

If your brake wear warning circuit breaks at the female connector on the hub where the brake pad plugs in do not buy the harness unless you have fatigue further up the wire. Instead buy the connector U1J0 973 802 (but check the number in your broken housing to be sure) for £2.01 plus VAT.

Each terminal is secured in the old connector by two very small barbs. I'm sure there must be a special tool that I don't have so I simply cut the connector from around the terminals a bit at a time using precision wire cutters. Insert both terminals into the new connector at the same time and secure both. There is a pink moulding inside the connector that I had to move with a screw driver before the brake pad connector would fully engage with the new connector.

Total job time 20 minutes and cost £2.41. Cheapest job ever on my A2.

 

[Binomio Karmesi]

Hi guys!

Our A2 showed this warning two weeks ago.

I went to VW-Audi oficial concession here in Valencia (Spain) to ask for an “oil level indicator” (I’m sorry but I don’t know how to say it in English) and I took advantage of being there to ask for the “brake warning” in cockpit. The answered me: “maybe you should change your brake pads (only, not brake pads and disks).
That was the push I needed to try to change brake pads myself.

But when I removed the wheel to start the change, I noticed the brake pads were mid-life-wearing AND the problem were in sensor.

Thanks to this topic I found the solution: not fixing the broken sensor because doing it the way you showed requires a master-mega-professional level, but buying the connector “1J0 973 80” (without “U”) in eBay to change this one for the bad-status-and-original connector (because I phoned VW-Audi garage and they told me I should buy a whole wire with the connector for 50€+VAT).

So... here I am. Expecting the connector from eBay and then, I will plug in the new to original electrical system. I will let you know how this adventure works out.

Regards!

 

[hotdog1]

I have this afternoon had a go at trying to get the small barbs into the new connector - i failed miserably and found it extremely hard to get either a good connection or for the male and female to fit back together, can anybody else chime in with their opinion or another way or tool to help this move along.....

thanks in advance

 

[spike]

A2 fixed



Each terminal is secured in the old connector by two very small barbs. I'm sure there must be a special tool that I don't have

Some info on the special terminal release tool here - https://www.a2oc.net/community/index.php?threads/home-made-terminal-release-tool.28715/post-234415

I made both sizes but did not bother with the fancy handles. Mine look more like a pair of tweezers but still work very well

Cheers Spike

 

[Binomio Karmesi]

Hi guys!

Sensor/connector 1J0 973 80 arrived yesterday. Came from https://www.ebay.es/itm/15254582896...04&_trkparms=gh1g=I152545828967.N41.S1.R2.TR2

Now it's time to cut the old wire with broken connector and weld the new one.

But how should I do that? I mean: both wires are blue-brow. Is it important? Is Polarity wiring something to having in mind before switching the soldering gun on?

Connector has figures 1-2 above entry of wires.... Maybe that is a clue... But I don't know how to take it...

Could you help me, pleas?

Thanks!

Regards!