Failed Brake Lights

I didn't think S1s got the dipping mirror, but if they did, why don't I have one!!?

Very true! If you fit a battery the wrong way round on a new car it will probably write it off!

According to my H Samuel everight Haynes manual (you may not be old enough to appreciate that) There appears to be a seperate pair of contacts on the ignition switch for the stoplights, dont ask me why, the supply goes from there to a fuse (F2) then to the stop light switch. The only thing between the switch and the lamps is the bulb failure module, if you havn't got the dot matrix display, you wont have one of these. I believe you said that there was 12 volts on the switch, if so that rules out the ignition switch and fuse. Assuming you have 12 volts coming out of the stoplight switch, and no bulb failure module, there must be a break in the wiring.

Peter.N.

I may be wrong, but I think the basic 2.0is still do the bulb failure warning, just they display it on the little car silhouette, rather than the dot matrix obviously. I do remember getting ( ! ) and the two rear lights on the car diagram more than once on my old one. They certainly do the startup brake light test anyway.
Unless it was an optional feature, but the rest of that car was fairly basic, so I can't see it.

Ciarán

This post has been edited by Ciaran on January 14, 2008 08:27 pm

Thats the way it is on my Presteige. I LIKE the little car sillouette btw.

I like the wee car silhouette too, its a pity it wasn't possible to have it as well as the dot matrix.

Ciarán

Well, if it has one, that would be a good place to look. I was just thinking that it's easy to find, its under the back seat....but no, I think that was on the CX. Does anyone know?

Peter.N.

I've also been told it's in the boot, behind the offside lamp cluster! I will check all these possible locations at the weekend.

Maybe in the meantime someone's got a Haynes or other workshop manual and would be kind enough to have a looK?

Haynes doesn't help I'm afraid, they dont give that sort of useful information anymore.

Peter.N.

Hi All,

There's a great deal of confusion in this thread with a few red herrings.

First of all we need to confirm something absolutely. Does the car have a Bulb Failure warning System? This is usually determined by the presence of the little silhouette of the car in plan view surrounded by LED's which light up to tell you which bulb has failed.

If it does have a BFS then the electronic unit (BFU) is located under the glovebox. Starting at the ignition switch the key must be round at the ignition position for the brake lights to work. Next after the ignition switch is fuse F2. Check fuse and test for 12v on the inlet and outlet. Next in line is the brake pedal switch. Check for 12v between terminal 1 on the brown connector and a good earth on the car body somewhere (even if you extend a wire from the negative terminal of the battery temporarily). Next, press the brake pedal and check for 12v on (outlet) terminal 2 of the 3-way brown connector. If no 12v on the outlet then the switch is U/S. Next is terminal 7 on the white connector on the BFU under the glovebox. With the brake pedal pressed and the ignition on there should be 12v at this terminal. Next is terminal 6 on the 8-way white connector on the BFU. Again check for 12v here. If 12v then the BFU is OK. If not, then the BFU is U/S. The next joint in the system is a white 4-way connector in either sill by the driver and passenger seats. If you can be bothered removing the trims and lifting the carpets then check for 12v on terminal 4 of each connector. Otherwise skip to the next test. Next in each case is the 4-way blue plug on the light cluster PCB. Check for 12v at terminal 1 in each case again with ignition on and brake pedal pressed. If 12v here then trace from terminal 1 to the bulb holder for the brake light. Check for 12v here. Next, with a known good bulb, insert it into the holder. Take the +ve lead of your meter and put it on the outer casing of the bulb. You should get 0v here and the bulb should be lit. If you get Ov and its not lit then the bulb is U/S. If you get 12v here then you're break is on the return/earth side somewhere so continue testing. Next put the +ve terminal of your meter on terminal 4 of the 4-way Blue connector. If no 12v here then break is between bulb holder and connector. Next, we're back to the white connectors in the sills. Terminal 1 in each case is the return. Test for 12v here. If 0v then break is between sill and rear cluster. This goes no where near the tailgate. Lastly the circuit terminates at body earth connector M5 which is located in the vicinity of the brake pedal. I can't say exactly where. Again test for 12v here. If you get 12v here then the break is on the earth connection itself.

In all of the above tests it is assumed that the ignition is on and the brake pedal pressed. It also assumes that the negative terminal of your meter is connected to the battery negative terminal for all tests. Only the +ve terminal should roam around the car.

If your car does not have the BFU then all of the tests above are still valid minus the two tests on the inlet and outlet of the BFU. Just follow the same sequence skipping the BFU tests.

On the basis that both lights are out simultaneously it points to the part of the circuit which is common. That rules out all of the wiring in the sills and going to the rear of the car. The failure is therefore most likely in the vicinity of the ignition switch, fuse, brake pedal switch or earth point.

Please carry out the above tests and let us know how you get on.

Cheers

noz

I've just got in from fixing the car, with the help of a friend, and here's what we found.

First, yes the car definitely has BFS. It doesn't have the dot-matrix display, it has the silhouette of the car.

We looked in all the locations that have been suggested as to the module's whereabouts, and it turns out Ciaran is right (thanks Ciaran!). Just unscrew the plastic panel above the pedals, and there are a few electronic components there.

One of them was dangling in space, with the connectors not properly pushed in. We pushed them back in properly and voila - a full set of working brake lamps.

It looks like there should be a mounting bracket which has broken off at some point. I didn't have any cable ties handy, but I'll tie it up with cable ties at some point (Sunday today so no chance of buying any).

In the end, a very easy fix!

Well done! Very satisfying isn't it.

Peter.N.

How very Citroenesque

Wouldn't you think the route would be something like 12v+, igtn, fuse, switch, lamp, earth! But then that's why we buy them isn't it?

Otherwise we'd all be running round in Ford Escorts . Err then again maybe not

At least they do have wires connecting everything together which you can eventually trace - unlike the new cars which have one wire and a computer to switch everything on!

Peter.N.

Glad you got it sorted Stu, as Peter says, its always very satisfying!

I must fix mine, MOT in a few weeks and the left one constantly fails now. Worst case I'll have to run some wires across from the right side as a quick fix in the mean time!

Ciarán

Well, I managed to sort mine last night.

I disconnected the light cluster, and brought it indoors to clean up the contacts, and inspect the tracks for any signs of breaks etc.

When I had it out in proper view, I noticed for the first time that there are actually two input sockets, both identical!
I couldn't see the difference between them at all, so after cleaning the contacts, I plugged the feed cable into the upper plug, where as it had been in the lower one previously. I had a wheel brace wedged on the pedal at the time holding the brake light circuit on, so as soon as I connected the plug, they lit up immediately! Result . I tried the old socket again just out of curiosity, and discovered that they actually function with the plug pressed halfway on, but once it is fully seated it looses contact again.

Whats this two sockets business about? (Not that I'm complaining, it saved me a lot of hassle).

The other odd thing I noticed, is that the two brake light bulbs on each side are different, one is a double filament, the other single, and the bases are different sizes. Is there any reason for this, is one used as the tail light as well? Seems quite a weird setup, but then again it is a Citroen... I found it quite amusing actually

Its soooo nice to be able to drive without a constant beep beep beep and message on the dot matrix

Ciarán