Brake warning sensor

[chic0821]

Car S63 AMG Coupe. I had the brake warning sensor come on recently. Pads were done about a year ago but as the car is on Sorn over the winter mileage done probably about 500 miles. Checked sensors, they seemed fine but as I was short of time to get new sensors I snipped off the ends & soldered the two wires together so that they should never flag up low pad warning (yes I know i have to change them, but forgot) Anyway everything sems ok until I have been driving for about 20/30 mins in town, then it flags up "check pads" warning. If I park up & return to the car the message has gone for another period of time Does something need reset by the dealer. Never had this before, normally change pads/sensors & everything is fine

 

[DSM10000]

Car S63 AMG Coupe. I had the brake warning sensor come on recently. Pads were done about a year ago but as the car is on Sorn over the winter mileage done probably about 500 miles. Checked sensors, they seemed fine but as I was short of time to get new sensors I snipped off the ends & soldered the two wires together so that they should never flag up low pad warning (yes I know i have to change them, but forgot) Anyway everything sems ok until I have been driving for about 20/30 mins in town, then it flags up "check pads" warning. If I park up & return to the car the message has gone for another period of time Does something need reset by the dealer. Never had this before, normally change pads/sensors & everything is fine

Isn't there a rear pad sensor as well?

 

[chic0821]

I did front & back

 

[Petrol Pete]

You snipped the wires and soldered them together ? Not sure how the car is wired up but that would mean you made a N/O contact into a N/C contact thereby completing the circuit as would have occurred when (if) the pad sensor wore on the metal disc face .

If this is the case the car 'thinks' the pads are worn .

I might be wrong ...it has been known

 

[ALFAitalia]

Certainly it is that way on most cars....to temporarily turn the light out I've usually just unplugged the sensor....no soldering required!!!

 

[Trickythemerc]

Soldering the wires is closed circuit so the warning will come on. Go back in and cut the wires to open circuit and see what you get.

 

[OneForTheRoad]

Wires need to be joined to turn off the light , open circuit puts the light on.

 

[chic0821]

You snipped the wires and soldered them together ? Not sure how the car is wired up but that would mean you made a N/O contact into a N/C contact thereby completing the circuit as would have occurred when (if) the pad sensor wore on the metal disc face .

If this is the case the car 'thinks' the pads are worn .

There is a continuous circuit when the pads/sensor are fine. The circuit is is broken when the sensor pad wears down, the wire is severed & you get the warning, so connecting the wires gives a continuous circuit. ie pads are fine. Looking at his video, he reckons it my be the connector

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[TC350]

Wires need to be joined to turn off the light , open circuit puts the light on.

Correcto mundo. When the sensor pad wears down by being in contact with the disc, it wears away the connection.

I suggest the OP orders new sensors from eBay, waits the day or two it takes for delivery, then spends a few minutes fitting them.

Sounds to me like the soldering skills may not be the best.

 

[OneForTheRoad]

Wires can be plastic coated .

 

[ALFAitalia]

When the sensor pad wears down by being in contact with the disc, it wears away the connection.

......but if that was the case surely the connection would still be made by the metal disc?? If it is the case...which it could well be as I've never looked into how they work on Mercs....its the opposite to every other cars I've had.....which either work by grounding a SINGLE wire though the disc to complete the circuit or connecting two wires buried in the pad or sensor, through the disc.

 

[OneForTheRoad]

......but if that was the case surely the connection would still be made by the metal disc?? If it is the case...which it could well be as I've never looked into how they work on Mercs....its the opposite to every other cars I've had.....which either work by grounding a SINGLE wire though the disc to complete the circuit or connecting two wires buried in the pad or sensor, through the disc.

Possibly momentarily if it all. What's been told to you is correct . No need to question it.

 

[OneForTheRoad]

There is a continuous circuit when the pads/sensor are fine. The circuit is is broken when the sensor pad wears down, the wire is severed & you get the warning, so connecting the wires gives a continuous circuit. ie pads are fine. Looking at his video, he reckons it my be the connector

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Pull the plug and bridge the pins , see if the light goes off , if yes then suspect it's the connector end at fault. and not the wiring loom on the car.

 

[ALFAitalia]

Possibly momentarily if it all. What's been told to you is correct . No need to question it.

Question EVERYTHING!!

 

[Mickyh7]

If there are two wires, the car may work out continuity, not just circuit/ short?

 

[OneForTheRoad]

Question EVERYTHING!!

Can't say I've noticed.

 

[TC350]

For under £9 and just a 3 day wait, why fart around?

Pardon our interruption...

 

[Muckypaps]

......but if that was the case surely the connection would still be made by the metal disc?? If it is the case...which it could well be as I've never looked into how they work on Mercs....its the opposite to every other cars I've had.....which either work by grounding a SINGLE wire though the disc to complete the circuit or connecting two wires buried in the pad or sensor, through the disc.

The circuit brakes while there is still some meat on the pads, you would have to ignore the light for quite a while before it touches the disc, if you’re still alive.
If you remove the sensor the light stays on as it’s open circuit.
The wheel sensor has a resistance value, so the ECU will not detect this value if the wires are simply connected together.