CX Brake Warning Wires - Re-routing

CX brake wear warning light wires are a constant problem. On all the CXs I've ever purchased these wires were broken or removed. If the wires are broken the owner never knows because the light will generally not come on. However, when the wires are removed I know the light was coming on, but falsely, and this is the mechanic's permanent remedy.

These wires light a warning lamp on the dash when the pads are worn to their minimum thickness. The lamp is lit by the wires grounding to the rotor, completing the lamp's circuit. This is a very effective method for warning the driver of impending trouble and saving the cost of a new rotor! The fact that it is troublesome is because few mechanics can be bothered to route the wires carefully when replacing the brake pads, and even when they do the wires still become chaffed and light the lamp falsely.

This page attempts to show a remedy for this arcane problem, for those who want to have everything working on their car, and working reliably. Clearances between the brake calipers and wheels are quite close, so the routing of the wires from the pads is critical. Also, the factory chose a wire path which results in breakage, no matter what is done to prevent it. I'm rather surprised a bulletin was never issued to correct this problem since nearly every car had to suffer it at some point, and surely Citroen dealer mechanics, and factory mechanics, must have noticed and commented on the problem. Oh well, we'll fix it for sure here.

original brake wires overview shot
As you can see, this path takes a bit of a circular route around the pivot of the lower arm and goes up the side of the 'tower' on the front sub-frame.

But the real problem lies in the bend at the lower ball joint. This photo clearly illustrates the problem because these wires are broken in the classic way.

Here we see an overview of the essentially original brake wire path. The wires are caught under the anti-sqeal spring (here a slight modification is made, a sheath keeps both wires together).

The two wires travel over the top of the spring as they leave the rotor area, a common mistake which will probably result in chafing of the wire against the wheel.

The wires connect to a pair of bullet plugs, then travel under a clamp and over to the other side of the steering knuckle, down the knuckle and along the lower arm.


If you cannot see the break clearly just click the photo to see a larger image (all the images are linked to larger copies). As you can see, this break is complete. We could fix it, but that really means running new wires since a fix in this stressed area will quickly break again. We could put a splice in the vertical section behind the brake duct (not shown) but again, we'll get the break again in a few years, or less at this very spot!

We need a good permanent solution and that means re-routing the wires to avoid this severe bend. The photos that follow show just such a route. Is it the only new route? No, but it has proven to work well on other CXs we own. We have actually used two different routes and are tracking their effectiveness over time, but this one mimics other cars where wires are taken out to the steering knuckle without failure (a French car at that!) and is the easiest of the two routes to run. See update below for our progress in monitoring the wire's longevity.

So here is the new route from the caliper. This is the opposite side's caliper on the same car, for reference. Also note the odd connectors, the previous owner's mechanic had completely removed the original wires. We are using standard bullet connectors found in any U.S. auto parts store. They have to be closed up slightly to grip tightly, and we'll be covering this connection with heat shrink tubing (it was left open for this photo). Notice the wires exit the caliper by passing under the spring.

If you don't have the original wires you may be a bit confused about how to wire them. Inside the engine bay are two wires, near the sub-frame, one green and one brown, twisted together. The brown wire runs ground to the steering knuckle and is bolted to the steering knuckle with the bolt holding the wire clamp (you can see the ring connector in this photo). The green wire runs to the pads, it splits into two connectors just after the wire clamp. Both wires run through a sheath.

In this route we've chosen to run the wire in front of the upper ball joint. This puts it perilously close to the rotor, so clamp it well to prevent movement. Since the wire and steering knuckle move together this does not pose too much of a problem.

Finally, the wire is run along the brake hose, wire tied to it in two places and also wire tied at the top, to the brake line. Simple enough, don't you think?


Recently we pulled the two front wheels off our CX Safari. One side, the passenger side, the wire ran loosely from the steering knuckle to the subframe, separated from the brake hose by about 3 inches. On the other side the wire ran alongside the brake hose, wire-tied to the brake hose. This wire run was broken at the last wire tie, which was on the brake line below the joint to the steel line. The break occurred because of another tight turn here. We'll be re-doing that wire to mimick the other side which as proven quite reliable. I will post photos of the two runs when I get them.