Problems with front and rear lights

Malfunctioning rear lights

The obvious suspects are the fuses, the bulbs and—especially if more than one light is failing—the ground. Removing the combination lights is easy: on Berline (Hatchback) models press the lens forward and simultaneously pinch the retaining clip firmly from within the luggage compartment, withdraw the unit, separate the lens and the bulb holder assembly by pressing the retaining catch; on Break (Estate) models raise the tailgate, remove the two lens securing screws, remove the screw retaining the assembly, then withdraw the unit.

If the corresponding left light works but the right one fails or vice versa, fuses are generally out of question (however, the tail lights feed through different fuses, LH tail light and number plate lights through F12 while RH tail light through F11). The current arrives behind the left rear light assembly, goes over to the right side, then comes back to be grounded with a bolt on the left side. Check the bulbs and clean the connectors in the light assemblies. If the problem still persists, undo the grounding bolt, clean the connections until shiny, spray them liberally with silicon spray and retighten.

Poor grounding often causes ghost lights: for instance, the stop lights flash together with the traffic indicators (often not at full brightness) or they go out when the indicator lights up, or any similar misbehavior. Just remove the left lamp cluster, undo, clean, spray with silicon and re-fasten the grounding bolt behind it. Clean all connectors of both lamp clusters.

If you didn't yet cure the problem, start to trace back the wiring. Although you have just cleaned the connectors and checked the bulbs (meaning that, if they don't work, the feed couldn't reach here), take the time to check the feeding connector of the left light assembly with a test lamp or voltmeter.

If you are surprised to find 12 V at the indicated pin, recheck the connectors and bulbs in the rear (bulb holders tend to corrode over time and will not work even if a brand new and perfect bulb is sitting in them), going through them all with a test lamp. If there is no voltage at this connector, go on to the specific troubleshooting section.

We describe the various circuits in a troubleshooting order rather than going through them blindly from the feed to the lamp. Some of the connectors involved are hard to reach and may require removal of internal trim parts. So, we should try to avoid unnecessary work by ruling out possible failures using easy checking points.

You should check every connector we mention with a test lamp or voltmeter, disconnect, clean and reconnect them firmly as you go along (even if they still make good contact, a little bit of cleaning pays off by helping you avoid many new failures in the future). Check that you still have the positive feed on every connection. When we speak about checking a fuse, do not only verify that it is still good but check with the lamp the socket which the fuse is seated in.

Rear foglights (Series I, before 1986)

Check the rear foglight warning lamp. If it lights up when you switch the foglights on, check pin 10 of I/3 (10-pin white). If your test lamp lights up there, only the flat grey cable going back to the lamps can be at fault. Alas, this requires the removal of many interior trim panels and carpets.

If the warning lamp is not lit, check fuse 11, then pin 3 of IV/1 (10-pin yellow). If you cannot measure 12V here but the feed is present at pin 10 of the same connector, you have to check the switch. As a quick proof, jumper these two pins: both the waring light and the rear foglights should work now.

For access to the switch, prise free the central panel of the left steering column switch [yellow], remove the two retaining screws now exposed, withdraw the central switch unit [green] and the selector control unit [red]. Prise free the upper and lower switches [blue] as well. Detach the connectors from the main loom and withdraw the multi-connector panel.

Rear foglights (Series II, after 1986)

Check the rear foglight switch. If it lights up when you switch it on, go to A.

Check pin 3 of the main board connector IV/1 (10-pin yellow). If OK, check Fuse 10. If OK, check pin 6 of II/1 (10-pin brown). ???

Either remove the instrument panel or try to prise free the foglight switch from the facia panel. The second solution is possible but difficult and carries the risk of damaging the retaining clips or the facia panel. Once you removed the facia, you can push out the switch from the rear while compressing its retaining clips.

A. The current does reach Fuse 10. Check pin 10 of I/4 (10-pin white). If OK, the next stop is already the connector at the rear, hence, the flat grey cable is at fault. Bother, this requires the removal of many interior trim parts.

Reversing lights

Look down between the battery and the engine, a little bit to the front, where the clutch cable passes over the gearbox (bigger models like BX 19 and GTi have lots of gadgets in the way). You'll find a switch screwed into the gearbox housing with two wires connected. Remove the wires, clean the connectors. With the ignition on, look for 12V feed in one of the wires (BX 14 models from 1988 have a mauve sleeve on this wire).

If you find the feed, go to A; otherwise, check Fuse 1 and pin 4 of V/5 (4-pin yellow). If you have a feed there, look for pin 2 of a 8-pin white connector (or pin 5 of a 7-pin brown connector in BX 14s after 1988) between the fuse and the switch in the gearbox. Either the connector or the wiring inbetween is at fault.

If there is no feed, check the other circuits from this fuse for correct functioning. If none of them works, you have a problem with the ignition switch or its connectors.

A. Reconnect the wire you checked for 12V in to the switch in the gearbox (doesn't matter to which output pin). Put the gear into reverse and check for 12V on the other output pin of the switch. If none, the switch should be replaced. You can replace it without draining the transmission (except for 150A and 150C engines), however, undoing it might require the removal of its environment for access, depending on the model (for instance, the air intake hoses block the way on fuel injected models). You could also try to reach it from beneath.

If the switch was OK, reconnect the other wire, too. Check pin 2 of V/5 (4-pin yellow) and pin 9 of I/4 [I/3 on pre-1986 models] (10-pin white). If no feed, look for pin 3 of a 8-pin white connector (or pin 6 of a 7-pin brown connector in BX 14s after 1988) back to the switch in the gearbox. Either the connector or the wiring inbetween is at fault.

From I/4 [or I/3 on pre-1986 models] the wiring goes straight back to the rear lamp assembly. If you have feed at the mainboard and none at the other end, the flat grey cable is broken somewhere. Alas, this requires the removal of many interior trim panels and carpets.

Stop lights

Locate the stop light switch beneath the footbrake pedal. Remove the wires, clean the connectors. With the ignition on, look for 12V feed in the green cable (later cars have a mauve sleeve on the wire).

If there is no feed here, check Fuse 3 and pin 1 of III/2 (6-pin brown). If you have no feed, probably the complete dashboard lighting and the screen washers/wipers are not working either. In this case, check pin 2 of IV/4 (6-pin yellow) and, finally, the ignition switch and its connectors.

But if you found current in the cable, reconnect this one to the footbrake pedal switch, leave the other alone and check for feed at the other output pin of the switch while pressing the break pedal. Your test lamp should light, or you have to renew the switch.

If you had 12V, reconnect the other wire to the switch and go on to pin 5 of III/2 (6-pin brown) and later to pin 6 of I/4 [or I/3 on pre-1986 models] (10-pin white). If you lost the feed somewhere, you have found the culprit. If you still have it at the last connector, then the flat grey cable going back to the rear lamps from here is broken. Alas, this requires the removal of many interior trim panels and carpets.

Tail lights

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