Interior lights in a c4

[GiveMeABreak]

Don't worry about that spare plug - it's probably a spare for unused kit. Just tuck the relay up behind the trim - the relay is likely to be the fan relay - pretty standard. It won't be for parking assistance - as that has a module in the boot if present.

[Cutac]

There is a module in the boot, but my car just has rear parking assistance.
I'll probably take my car to a dealer to reprogram the BSI since BSI doesn't seem to be defective.

[GiveMeABreak]

Best to just get it diagnosed full stop and see what errors there are coming up. If we had the codes it would help troubleshoot.

[Cutac]

A small update.
I've contacted the previous owner and he says nothing was tampered around the dome light. Or at least what he knows of because something was definitely done since wrong fuse was in place.
I probably won't have enough time to take it to an electrician this week, but it was once at the dealer for that and after an hour their electrician said it needed a new BSI. Which I hope isn't true, and honestly don't think it's actually BSI at fault since map lights are working which are on the same jack.
My best bet is that a wire is damaged somewhere because voltage readout was dropping over time from 5V to 0V.

[GiveMeABreak]

Don't forget that the voltage drop is likely to be either down to the timing of the courtesy lights (that are supposed to dim after a certain time lapse) or because of energy management / Economy Mode.

The BSI is an ECU - and very sensitive, so can be easily damaged - it is possible that the BSI is working on most circuits, but may have an issue in another area.

I still think you need to test the connections individually using the wiring diagram I posted - but take account that the courtesy lights are timed - opening / closing doors or after a certain amount of time if the door is left open for energy management.

Ideally, put the lamp permanently on (but be aware economy mode will still turn if off after a certain time) and then test the circuits / wiring one by one taking into account the above.

[Cutac]

I've measured voltage wity the car running to avoid Economy mode.
I've planned to test wiring using setting on my multimeter which makes a sound when there's a short. Problem is that I can't find thst jack on the BSI.
I don't think it's a grounding issue since those lamps use same grounds as door lights which work.
Could you please take a look at the diagrams and say if map lights use same power wires as dome lights?
Also, could rear dome light be a cause in any way?

[GiveMeABreak]

If you look at the diagram, the power is the same - however, depending on the where the courtesy light switch is set - left, middle or right, will depend on what circuit and therefore bulbs are powered - On when a door or boot is opened for 30 seconds, or when the car is locked; Permanently Off; Permanently On.

So if you have the engine running and have it set to permanently on - you will get a feed, but on either of the other settings, it will be permanently switched off, or will be timed depending on doors or timing.

You can see this on the circuit diagram where the position of the switch is moved left right or centre as to how the circuits are controlled. The BSI on 301 is for time delay and command of the circuit

[Cutac]

I've been looking at the diagram more thoroughly and I've made some conclusions. But first, English is not my native language so I might make some mistakes and second, I'm a mech. engineer, I don't know a thing about electricity

As I can see, front and rear dome light share the same +(AE07B BSI Accessory + Output) but a different - so they can be operated independently. Correct?
Next, front map lights use the same +(AE07B BSI Accessory + Output) and the same - (300 Front Interior Lamp Control) and the same ground(MC301 Earth Mc301) as does the front dome light. There is a fourth wire(301 Courtesy Light Time Delay + Command) which I assume is not relevant for what I'm on about. It is used so that the BSI can decide when to switch it on, right? Which means, even if it was cut off, light would still have to come on using the hardware switch, right? Following, if map lights work, which they do, and since they use the same +, - and ground as the dome light, shouldn't the dome light be working?

After looking at the diagram thoroughly and with my understanding of the wiring, I honestly can't understand why doesn't the dome light work.

[GiveMeABreak]

Wire 3020 is for the rear interior lamp control.
Wire 300 is for the front interior lamp control.
AE07B and C are the same BSI accessory + output.

Front MAP lights:
AE07B is the same and is the BSI Accessory Accessory Positive (+)
MC301 (Earth) is the ground

So to answer your question, 300 is NOT the same as the wires do not intersect (join). AE07B and MC301 make the circuit as these are on or off when there is power (ignition on / engine running) when the map light switch is on.

Your English is fine.

[Cutac]

Alright.
What does "lamp control" actually mean?
So, what all 4 bulbs on the ceiling have in common is just AE07B and C which should be alright since at least one bulb connected to it works(map lights). Ground on both front and rear lamps should be alright since other devices using those grounds work.
Which leaves 3020, 300 and 301 in question.
Am I correct now?

But if AE07B and C work(given that map lights work) and ground are good(given that door and boot lights work), why don't dome lights work?
What do "Front Interior Lamp Control" and "Courtesy Light Time Delay + Command" do?

And thanks for being patient with me

[Cutac]

Hello again.
I've acquired a Diagbox interface and software and I've found a single fault with my VTS. It says 'F993 Engine Fuse Box: Lights Dimmer Fault'
Could that be the cause of my lightning problem?
Can anyone shed some light regarding that fault(pun not intended )?

Thanks

[GiveMeABreak]

I’ll check on the fault code tomorrow, but if it is pointing to the engine fuse box, then rheas probably not a lot you can do except replace the whole thing as these are not repairable to be honest. I’ll see if there’s any more info on that code first though.

[Cutac]

Alright, thanks
Also, is there such thing as an ECU for directional headlamps? I thought BSI and headlamps communicate directly, without an additional ECU.
I was trying something in Diagbox and have gotten directional headlamps ECU error. It went away, but I'd still like to know if there is in fact a physical ECU.

[GiveMeABreak]

Hi

Yes there is a separate ECU. If you look at the post in the following link, I have put up the flowchart for somebody thinking about a conversion, which is not really practical. If you look in the table for 6608 that is the Directional Headlight ECU, which is separate to the BSI.

viewtopic.php?f=3&t=60287#p577335

Here's the ECU, shown at (2)

[Cutac]

Thank you very much Marc

Found anything useful for dimmer fault?