Rear/Tail light problems

[Citran]

Hello!

I have a 1992 Citroën BX Millésime 1,6i, and I’m experiencing an issue with the rear/tail lights.

The reverse light and brake light are working, but the license plate illumination and rear tail lights are not. The indicators (turn signals) and hazard lights are functioning (assuming they operate on a different circuit?).

I’ve measured the fuse box and found no power on the last row of 5A fuses. How are these powered?
I’m wondering if the issue could be related to the ignition switch, as the front position lights are not working either.

Does anyone have any thoughts or ideas? Is it possible to test the ignition switch and the current from it?
The only other issue I’ve noticed is that the hazard lights are a bit slow to start, and the relay makes a “screeching” noise when it activates.

Any advice or suggestions would be greatly appreciated!

[David]

It sounds like a switch fault to me. If you look at the back of the switch, there are 2 plugs, one with 6 thin wires & one with 4 thick wires, this is the plug that you’re interested in, one wire is constant 12v live, so for a quick test, just put a piece of wire between them until you find the wire that operates the position lamps, I think it’s if you link the two top wires, if I remember correctly, then they should come on. You can also see if you get power to the fuses at the same time.

BE CAREFUL, as there’s constant 12v live here & no fuse, so if it shorts, you could have serious consequences!

It won’t have anything to do with the ignition switch as the lights don’t go through it.

As for the hazard lights being slow & screeching; that’ll just be the flasher box in the fuse box. It’ll just need replacing.

Hope that helps.

[Citran]

Thanks for the quick and detailed reply!

If I understand you correctly, you're referring to the steering column switch/indicator stalk? I will try to unscrew it and bridge the connection. Just to be clear, the high and low beams are working without any issues.

If it turns out that the issue is with the steering column switch, I will replace it. My next question is whether the same switch fits all Citroën BX models? It doesn't seem to be much of a price difference between a good used switch and a new one when I compare between car wreckers and parts suppliers.

Here’s an example of a steering column switch from a brand I usually use for sensors when they’ve broken on the car. Am I on the right track? https://www.autodoc.co.uk/valeo/1072476

[Citran]

So!
I have now measured and bridged the contacts to see if it’s possible to manually activate the position lights.
Unfortunately, I didn’t succeed, but it’s still a step forward.

The connector with four pins has the following functions:
Blue (12 V)
Green (buzzer)
Yellow 1 (low beam)
Yellow 2 (high beam)

The connector with six pins has the following functions:
Blue (12 V)
White (unknown)
Gray (horn)
Yellow (turn signal)
Green (6.7 V/relay)
Yellow (turn signal)

I couldn’t find any function for the white contact, and I didn’t hear any relay clicking when I bridged the contact.

I’m skeptical about the green contact since it gave a low current, 6.7 volts. It also activated (clicking) a relay near the fuse box, but I couldn’t identify which one. However, I couldn’t determine that any function was activated when bridging the contact.

I measured the last four fuses (5A) in all configurations, but there was no current on them. This means no power is reaching the fuse box and being distributed to the lights. Occasionally, when measuring the mentioned fuses, I got 0.05 V on the last three fuses. Not sure if this was due to my cheap measuring instrument or if there was indeed a weak current on them.

There’s also a switch (push/pull) in the "cockpit" that I suspect is a aftermarket construction. I don’t know its function, but if I were to guess, it might be for low beam automation? I’ve never used it and didn’t find any function connected to it, but it might be a potential source of the issue. However, the switch has been installed for as long as I’ve owned the car.

I tested all configurations with the ignition in different positions, except with the car running. No diffrence.

If anyone knows the function of the green- and white-marked cables, I’d be very grateful—or if you have any tips on what the fault could be. For now, I’ve probably ruled out the turn signal lever!

[David]

From what I remember, there should be another thick yellow wire going to that position in the 4 pin plug wheee your thin green wire is. It’s possible that someone has rewired the car. The buzzer also is to warn you that the lights are on with the ignition off, but should be connected to the position lights somewhere. All 4 wires go down to the fuse box, but I don’t remember which positions.

The green wire that you asked about is your flasher box for the indicators. If you connect it to any of the indicators (or the horn), it will turn on & off like it does in general use. That’s why it clicks.

The white wire that you’re unsure about is the feed to the rear fog light switch. If you send 12v down it, then the rear fog lights will work with nothing else turned on.

I’m not sure what that lever switch is for, as that position is only used for the choke on early petrol cars, but maybe they’ve connected the position lights to it?

I’d personally check the back of the lights switch with a multi meter to see if the switch connects the blue & green wires in the 4 pin plug when turned to the 1st light position, but I suspect it won’t. Then I’d have a look at that switch that you suspect is aftermarket to see if that is working the position lights.

Hope that helps.