Diagnosing the door open warning display

[Jugostran]

Hello everyone!
So, I have been tinkering with the door open display, and I am currently stuck in a diagnostics mess. I have determined that the board itself is fine (along with all the bulbs), but unfortunately, it only ever displays the rear right door as open. It is quite puzzling since it's also meant to indicate when the lights are on. So yeah, I am quite stuck. I don't know how to diagnose the issue. If anyone has previously dealt with this, any input would be greatly appreciated

[white exec]

from Haynes (1995 edn) p.418

The doors open display (#940) looks to be directly driven from a common IGN+, with each lamp connected directly to Gnd by each door etc switch.
You should be able to bench-test it off the car. Pin numbers on the diagram.

I don't think it displays "Lights on", although the circuit shows it does have instrument panel illumination.
"Lights on" warning on BX is usually the audible buzzer (in the steering column shroud).

If the display checks out, and the door switches operate the interior lights properly, the intermediate connectors (between display and door etc switches) may be misbehaving.
EDIT: Ignore this last paragraph, it's not correct. See below...

[Jaba]

I think you will find that these indicators are illuminated by a switch on each door handle. The door pillar switches are for the interior lights only.

It seems unlikely that 3 out of 4 door indicators would fail concurrently so the problem must be in the board, but I see you have checked that out, or if the bonnet indicator works the 5 way white connector and I don't know where that connector is exactly. If you can locate that in the harness somewhere then it would be a good testing point.

I bought a Xantia once to replace a BX and it did not have that door open indicator and I really missed it.

[white exec]

John is right. The switches in the diagram above are "door lock switches".
The interior lights are brought on by the separate door-pillar switches, #230, 231, 232, 233.

Have you powered up the indicator unit on the bench, and tested each channel?

[Jugostran]

All of this is super useful info. Thank you!
Also, I should have pointed out that the board for the lights was replaced, and it still only illuminates that one door.
I will try to diagnose the connection between the door sensor and the end of the cable.
However, quick question, where is it's exact place of the sensor for the door? I theorize it may be oxidized/dirty.

[white exec]

On the bench, do all the channels (4 doors, bonnet, and boot) on the indicator board work, when each one is grounded ?

[Jaba]

All of this is super useful info. Thank you!
Also, I should have pointed out that the board for the lights was replaced, and it still only illuminates that one door.
I will try to diagnose the connection between the door sensor and the end of the cable.
However, quick question, where is it's exact place of the sensor for the door? I theorize it may be oxidized/dirty.

Its part of the door handle itself and requires inside door panel removal.
Does the bonnet open indicator work?? I ask this as it uses a different circuit and does not come through the white 5 way connector in the harness that I mentioned earlier as a good testing point (when located that is).

[Jugostran]

All of this is super useful info. Thank you!
Also, I should have pointed out that the board for the lights was replaced, and it still only illuminates that one door.
I will try to diagnose the connection between the door sensor and the end of the cable.
However, quick question, where is it's exact place of the sensor for the door? I theorize it may be oxidized/dirty.

Its part of the door handle itself and requires inside door panel removal.
Does the bonnet open indicator work?? I ask this as it uses a different circuit and does not come through the white 5 way connector in the harness that I mentioned earlier as a good testing point (when located that is).

Neither bonnet open indicator nor the boot open indicator work. Only the rear right door works, as mentioned before.
Luckily I have sourced a multimeter which might make diagnostics a tad bit easier (even with my severely limited electrical knowledge ).
Also, I still need to locate the white connector. Thankfully I have become quite well experienced in taking the interior apart (I sometimes do it out of boredom when waiting for someone xD) so finding it (assuming I find the rough area where it is located) should be easy.

[Jugostran]

On the bench, do all the channels (4 doors, bonnet, and boot) on the indicator board work, when each one is grounded ?

I tested continuity. Both boards tested good.

[white exec]

Have you tested the display unit on the bench yet?
Supply it with 12v, and then Gnd each of the door etc channels in turn, to make sure each one illuminates.

Our posts crossed!
When you say you have continuity, are the individual lamps actually lighting when supplied and Gnd'd as above?

[Jugostran]

Have you tested the display unit on the bench yet?
Supply it with 12v, and then Gnd each of the door etc channels in turn, to make sure each one illuminates.

Our posts crossed!
When you say you have continuity, are the individual lamps actually lighting when supplied and Gnd'd as above?

Yes. The board itself is tested all good (including the connector on the back). The issue probably lies somewhere between the door/bonnet/boot and the end of the cable that connects to the display.
EDIT:
Some new discoveries. The only pins with any voltage on the board are (when looking right to left when display is mounted upright in the car) the first two (the ones lighting up the rear right door), and pin number 9 (also looking right to left). And another minor correction - the lamp that lights the entire display with a green glow also works.

[David]

The best thing that you can do is find the white connecter behind the glove box and start diagnostics from there.

The pins need to be earthed out to test them. I think the bonnet one goes in the grey connector, not the white one, but it should be easy to find as all the wires are all thin, and either dark green or orange. The said connecters are different to the rest on the car, so they're obvious when you find them. The bonnet switch is probably full of corrosion & faulty. The connections aren't the best in the white connector, so the wires could've snapped, especially if someone's been messing behind the glovebox.

Pull the glovebox out and see what you find.

Hope that helps.

[Jugostran]

The best thing that you can do is find the white connecter behind the glove box and start diagnostics from there.

The pins need to be earthed out to test them. I think the bonnet one goes in the grey connector, not the white one, but it should be easy to find as all the wires are all thin, and either dark green or orange. The said connecters are different to the rest on the car, so they're obvious when you find them. The bonnet switch is probably full of corrosion & faulty. The connections aren't the best in the white connector, so the wires could've snapped, especially if someone's been messing behind the glovebox.

Pull the glovebox out and see what you find.

Hope that helps.

Hey there,
Hugely sorry for the very late reply, but I have been really busy nearing the end of 2021. Anyway, this sounds like a good lead as to fixing my issue. One small question, is this connector also located behind the glove compartment on left hand drive cars? I'll be tearing apart the instrument cluster to replace the bulbs soon, so if the LHD ones have it on the left, I could possibly also diagnose the door open display.
Either way, I am very thankful for your advice!