On my 94 E320 (w124) the brake pad wear indicator light has been on since I painted my calipers - I've checked the pads and they're good so I've been ignoring it for awhile. Today I investigated further:

- unplugged 4 front sensors -- light still on
- unbolt the 2 front sensor holders -- light off

SO - I looked at the sensor holder and it appears that it makes electrical contact with the caliper itself.

- clean passenger caliper at the contact location and clean contact
- attach sensor conector and 2 sensors -- light still off
- repeat on drivers side -- light comes back on

Can someone tell me how this circuit is suppose to work? Why is the light on (even though the two sensors are unplugged at the drivers side)?

Thanks!!

EDIT: See attached photo - #5, 10 and 15 are the parts I'm talking about.

My retaining screw is quite rusted - I think I'll change that and see if it makes a difference.

EDIT2: Changed the screw - no change in the symptom. I think i'll trace the connector back and see where it leads.

Attached Thumbnails

 

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE