Carpokes

Trying to get rid of all the old & broken wiring for the brake pad warning system

A while ago, I removed the wiring from the front left brakes to the engine compartment, loop-connected the harness-side connector, and the dash light went out

Now I've done the same for the right side and the light is back on the dash

What am I missing? How do I fool the system and get rid of the dash light for good?

1988 951 No ABS

The sensors just create continuity between the two harness wires unless/until they wear down and break/open the connection. If you connect the two sensor wires in the harness on both sides, that should do it. If the brake light is still on, either something else is triggering it, or you may have an issue with the connector or wires upstream from where you shorted it...

There must be more to this story: the amount of wires doesn't add up

The sensor is basically one wire in a loop? Why then so many wires coming to the harness only to terminate into a 2-prong plug?

Same on ther side

For months, the light stayed off with driver's side harness shorted

I tore out the passenger wires the other day (fender cover off and might as well clean up all these dried out crumbling wires) and shorted the harness plug

Light comes on

This is clearly more complicated. Something to do with ground? Each harness plug has a ground connection next to it. Why?

...and out of the plug is a ground wire attached nearby...

With all the wiring intact, you can just short the ends of the individual sensors. Looks like you removed some of the harness, where you are probably getting into trouble. I'm guessing your shorting wires on that side are not picking up the two wires at the end of that sensor (?). If you cut the end of the senor off and find the two wires that get disconnected when worn, you could then ohm them out to the wires you need to connect in the remaining harness, if that makes sense.

The sensors are wired like old-school Christmas lights --in series-- so that if any one goes out (wears down), the entire circuit is open and the dash light goes on. As best I can tell, with only moderate confidence, those wires are just creating that in-series circuit so that the cluster doesn't need multiple inputs. The extra ground wires appear to ground the wheel assembly and side markers. Looking at the schematic, it looks like you can bypass all 4 sensors by connecting the brown wire with white stripe in the front right harness with the brown wire with red stripe in the rear left sensor harness. Doing that would bypass all 4 sensors. You can get to both of those wires easily at the cluster -- they are pins 6 and 7 of the A edge connector. Basically, if pins 6 and 7 are not connected (via all 4 sensors in series, or bypassed) the light goes on. If you were to short those two pins together, based on my reading of the schematic, it should bypass all 4 sensors. Never tried it though... I can test that on a spare cluster if helpful...

Ok I'm confused

I feel we are confusing terms

Here are the harnesses:
And here is what I am calling the sensor wire:
I have removed all the wire up to the harness. The wire had connections at the strut and on the body behind the strut

Starts as you say 2 wires at sensor end.. connects to a 5 wire loom at strut.. the 5 wire loom goes up into the engine bay.. and plugs into this:



The ground wire comes out of the loom plug and grounds at the body

Nothing else connects here--no lights, etc

This is repeated identically on the other side

Now.. explain the Christmas Tree

Re the Christmas tree -- think of it like one continuous wire with four switches (i.e. sensors) wired in line, so that if any one switch is off, the wire is broken. What i can tell you for sure is that the each sensor is nothing but two wires that are connected at the end unless/until the sensor is worn down. As long as all 4 sensors are intact (unworn), the circuit acts just like the Christmas tree --i.e., all switches are on and the wire connects cluster A pins 6 and 7 together so the warning light stays off. If any one sensor opens, the connection between pins 6 and 7 is also broken, and the light goes on. You should be able to bypass all of your frayed harness wires by connecting 6 and 7 behind the cluster. Or if you want to do it under the hood, I'd cut the sensor off the very end of the wear sensor to get access to those two wires. Then use a multimeter to trace those two wires back to the barrel connector where you are making the short, and short the two terminals that connect to the two wires in the sensor. If you already did that and the light is still on, there is some other break in your Christmas tree string. Cue Clark Griswald.

Those barrel connectors under the hood are used for both the brake sensors and the ABS system (if equipped). I'm an '86 guy so can't go out and confirm, but I'd assume the extra wires are for the ABS system you don't have. If you clean them off and give me the wire colors I can confirm against the schematic -- but that's mostly for academic curiosity.

Ahh now I get it

Even though ABS is available by 1987, my car does not have that option

What confused me was my "barrel" connector isn't a barrel like ABS cars; it's a flat 2-input receptacle

Now I understand that the long middle section of the wiring loom has five wires because they use that same loom for ABS

And I am guessing that those grounds simply ground the unused ABS wires from the loom

The only question is why, when I short both "barrels", does the light come on?

When one barrel was shorted, light went out

Now that I've disconnected the other Christmas Tree light & shorted its barrel, light is back on



FYI the rear sensor wiring is still present.. unsure of its condition. Maybe I should find their barrels and short them too

All this time you could have just pulled the cluster and removed the bulb

AudiSport wrote: Wed Apr 15, 2026 8:44 am All this time you could have just pulled the cluster and removed the bulb

Another time-honored approach.