Unknown wire in Left front wheel well.

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Austintatious
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Unknown wire in Left front wheel well.

Post by Austintatious »

So I found a 2 conductor cable with a thick rubber insulation coming out of the same hole as the ABS wheel speed sensor. Someone has cut it. I have no idea where it goes. It had grommets on it that engage metal holes to secure it right along side the ABS wheel speed sensor wires...

The thing is, I have no idea where this cable is supposed to go. Examining the back of the brake assembly I can find nothing that it might go to. It is just sort of there, but it looks like provisions were made for it... So I am at a complete loss. The passenger side does not have this cable.

Any Ideas what this is?

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sharkfan
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Re: Unknown wire in Left front wheel well.

Post by sharkfan »

Brake pad wear sensor - also on the right rear.
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Austintatious
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Re: Unknown wire in Left front wheel well.

Post by Austintatious »

sharkfan wrote: Tue Feb 08, 2022 8:50 pm Brake pad wear sensor - also on the right rear.
thanks... I have one on the way, but The connector on this is MIA so I don't know what I will do.
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Re: Unknown wire in Left front wheel well.

Post by GRNSHRK »

That's messed up that somebody would just cut that off [-X

Any chance you can follow the harness from the inside and see if also connects to another harness [-o<

May be time for custom wiring :-"
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Austintatious
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Re: Unknown wire in Left front wheel well.

Post by Austintatious »

I need some more help here guys....

Turns out whoever cut the front sensor wire also cut the rear :evil:

So my issue right now is that the sensors themselves have only 2 wires going to their waterproof connector. However the cut wire has 3. One of them is a ground wire. Since both are cut I have no idea where the ground wire is supposed to connect to.

Can anyone take a picture of how this stuff is supposed to go in? I cannot find anything online.

I was able to buy a pair of wear sensors and modify one so that it forms a proper connection that I can splice into the existing wires. I just need to know where to ground this. I cant find any place obvious.

I am further confused on how these sensors actually work. I found where they snap in on the brake assembly, but how they sense wear is beyond me... I am just curious about that.

Any help really appreciated.
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RossDinan6
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Re: Unknown wire in Left front wheel well.

Post by RossDinan6 »

What year? The pad wear sensor opens when it wears on the rotor due to worn pads. Two wires on my '84. Twisting them together shuts off the light in my case. I've never looked at a later ETM but maybe a third wire is a shield, seems unlikely to me though.
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Austintatious
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Re: Unknown wire in Left front wheel well.

Post by Austintatious »

RossDinan6 wrote: Wed Mar 09, 2022 1:10 am What year? The pad wear sensor opens when it wears on the rotor due to worn pads. Two wires on my '84. Twisting them together shuts off the light in my case. I've never looked at a later ETM but maybe a third wire is a shield, seems unlikely to me though.
it is an 86'

The third wire is definitely not a shield.. in the electric troubleshooting manual it shows a ground wirein the same bunch as the other 2.

I connected the wires up and put an O connector on the brown wire and found an empty screw hole to bolt it to... that should ground it out proper.

Ill have to do the same thing with the rear when I get the other 2 wear sensors I ordered.

The wear makes sense to me now... THe pads are real thick so I couldnt see how this was sensing anything... after looking closer I can see that as they wear, eventually they will hit and wear through the lining sensor and make a connection.... So in essence the sensors are throw away.
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Re: Unknown wire in Left front wheel well.

Post by hornhospital »

Actually, they wear through and break the connection. The wear sensor when unworn completes the circuit. Breaking the circuit activates the brake lining warning.
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Re: Unknown wire in Left front wheel well.

Post by plip1953 »

hornhospital wrote: Thu Mar 10, 2022 2:56 am Actually, they wear through and break the connection. The wear sensor when unworn completes the circuit. Breaking the circuit activates the brake lining warning.
I'm not saying the above isn't correct, although my understanding has always been that on older BMWs like ours the warning light illuminates as a circuit is completed once the wear sensor makes direct contact with the disc surface. And that the warning light only illuminates when the brakes are being applied, thereby differentiating that being the issue as opposed to low brake fluid or handbrake applied (constant warning light illumination). Have I simply been wrong all these years?
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Re: Unknown wire in Left front wheel well.

Post by 86_6series »

My understanding is the same as Phil's.
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hornhospital
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Re: Unknown wire in Left front wheel well.

Post by hornhospital »

Since both of my E24s are Series 2, I don't know if the Series 1 system makes or breaks the connection to indicate a worn out pad. Check the continuity of your new sensors. If they show no continuity, they indeed would close the circuit when wear allows it to contact the rotor. If they show continuity through the sensors, they operate as I said.

Now I'm confused....
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Re: Unknown wire in Left front wheel well.

Post by hornhospital »

Here are screenshots of the pad wear indicator system in a 1984 633CSi. I don't have the ETM for any earlier models. Note that either breaking the circuit OR grounding the sensor will light the warning indicator.
20220310_120223.jpg
20220310_120223.jpg (330.04 KiB) Viewed 2113 times
20220310_120255.jpg
20220310_120255.jpg (549.63 KiB) Viewed 2113 times
Ken Kanne
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RossDinan6
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Re: Unknown wire in Left front wheel well.

Post by RossDinan6 »

hornhospital wrote: Thu Mar 10, 2022 2:56 am Actually, they wear through and break the connection. The wear sensor when unworn completes the circuit. Breaking the circuit activates the brake lining warning.
Feel free to reread my post. It seems I neglected "or shorted". The post was still accurate.
Ross
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