Luggage compartment/boot light not working

[rich11235]

Hi, anyone know how to get the boot light to work on T5.1 Cali? I have checked the bulb and it is intact. For some reason it seems to have a diode in parallel with it which is a bit mysterious. I suppose it is supposed to come on when the tailgate opens. But I'd have thought if the tailgate door sensor/switch (where is it?) had failed I'd get all kinds of other warnings (door open etc.)

Any ideas/help gratefully received

TIA

 

[WelshGas]

Hi, anyone know how to get the boot light to work on T5.1 Cali? I have checked the bulb and it is intact. For some reason it seems to have a diode in parallel with it which is a bit mysterious. I suppose it is supposed to come on when the tailgate opens. But I'd have thought if the tailgate door sensor/switch (where is it?) had failed I'd get all kinds of other warnings (door open etc.)

Any ideas/help gratefully received

TIA

It’s not a simple On/Off system. It is timed and normally switches off after about 10-15 minutes if the tailgate is open.
i think it is activated via the BCM, Body Control Module, which monitors the Rear Tailgate Lock system.
Does the bulb actually work or just looks intact?

 

[TripleBee]

Can you see your bootlid showing open on the instrument cluster?
Like in this thread:

Door Open Warning

Just noticed today that when my tailgate is open, it doesn't show on the MFD display....whereas as the other doors do (when open). Is the tailgate meant to show on the MFD?:thumbsup:

www.t6forum.com

If not, you will not get a warning, error, light, ... as the van doesn't know the bootlid is open. The microswitch should be in the lock itself.

 

[Drpps]

Do the other lights by the footwell come on when you open the drivers door for example or is the overhead switch set to 0 rather than the open door sign? Not sure if that would also disable the boot light.

 

[rich11235]

Thanks guys. Come to mention it I don't think I have noticed the tailgate showing open in the MFD (only had the van a few days!) So I will check the microswitch in the lock (is it hard to get at?)
I already put a multimeter across the bulb and it had low/zero resistance. Still can't work out what the mystery diode is for

 

[flying banana]

iftheres a diode in the circuit then maybe the bulb is polarity sensitive as some l.e.ds are. try it both ways round. the bulb that is

 

[WelshGas]

iftheres a diode in the circuit then maybe the bulb is polarity sensitive as some l.e.ds are. try it both ways round. the bulb that is

In my T5. 1 the bulb is not Led just a standard 5w festoon bulb. Could have been changed by previous owner. Can't say I noticed any diode.

 

[flying banana]

In my T5. 1 the bulb is not Led just a standard 5w festoon bulb.

not looked at mine. I read somewhere once that some led bulbs fit both ways round but being a diode they are polarity sensitive. could be a fuse ? is everything else working ? ie wiper/washer etc ?

 

[Wesel]

Astonishing if there is a diode that it is in parallel, and not in series! Could we have a close-up photo?

 

[rich11235]

Astonishing if there is a diode that it is in parallel, and not in series! Could we have a close-up photo?

You are right it is in series actually, it's a normal filament bulb not a LED. Anyway, as per earlier recommendation I checked and tailgate is not showing on the MFD as being open so I suspect it is the microswitch. Anybody know how to get to it?

 

[TripleBee]

Unscrew both bolts with this:
probably M8
Then you get this:

Gently try to get it out of the bootlid, but watch out for wires and possibly a rod (maybe not).
The switch will be on the black plastic with the 3 pin connector.
Don't know if you can get the switch out.

Then you can test it by shorting 2 pins (but I don't know which ones).

 

[WelshGas]

View attachment 60446
Unscrew both bolts with this:
View attachment 60445 probably M8
Then you get this:
View attachment 60444
Gently try to get it out of the bootlid, but watch out for wires and possibly a rod (maybe not).
The switch will be on the black plastic with the 3 pin connector.
Don't know if you can get the switch out.

Then you can test it by shorting 2 pins (but I don't know which ones).

Is this microswitch just for the boot light or does it also tell the BCM if the tailgate is open or closed?
The OP has said the tailgate shows closed on the MFD.

 

[TripleBee]

It gives signal to the BCM, and that triggers the light and the MFD I think.
Don't think there is a direct link between the light and the lock. Otherwise your light would stay on forever if you leave the bootlid open.

 

[WelshGas]

It gives signal to the BCM, and that triggers the light and the MFD I think.
Don't think there is a direct link between the light and the lock. Otherwise your light would stay on forever if you leave the bootlid open.

If that’s the case then the micro switch must be working as the MFD shows the tailgate is closed.

 

[rich11235]

Thanks TripleBee, looks pretty clear. I must say I would never have gone looking for the switch on the actual tailgate. Surely would make more sense (reduce number of wires passing across the tailgate to body connection) to put it near the lock plate or on the slam panel/cill where they used to be on "old" cars. Anyway, I will investigate

 

[TripleBee]

If that’s the case then the micro switch must be working as the MFD shows the tailgate is closed.

Is the switch normal open or normal closed?
When the bootlid is closed (most of it's lifetime) I would put in a normal open switch. When you open the lid, the switch is activated, giving a current due to a short circuit. This triggers the BCM and all the rest.
If the switch stays open when you open the lid, nothing happens and no one knows the lid is open.

 

[WelshGas]

Is the switch normal open or normal closed?
When the bootlid is closed (most of it's lifetime) I would put in a normal open switch. When you open the lid, the switch is activated, giving a current due to a short circuit. This triggers the BCM and all the rest.
If the switch stays open when you open the lid, nothing happens and no one knows the lid is open.

In that case the Tailgate would not show Open on the MFD when it is in fact Open?

 

[TripleBee]

If the switch is actuated by opening the bootlid, and the switch is broken, or does not get actuated because of any malfunction, nothing will go to the BCM. Then the vehicle doesn't know the bootlid is open, and there will be no light, no display, and best of all, the vehicle will close itself again after 30 seconds, because, for the vehicle, you didn't open the boot.

Maybe that is not so easy to understand if you are not really into electrics?

See it as an old door switch. If you open the door, and the switch spring is broken, the switch will not extract to make contact, and the inner light will not go on.
Here it can be the same, but on electronic level. The principle stays the same, just the design is different.

 

[rich11235]

In that case the Tailgate would not show Open on the MFD when it is in fact Open?

Which is what's happening. Tailgate never shows open on MFD even when it is, and luggage compartment light never comes on

 

[WelshGas]

Which is what's happening. Tailgate never shows open on MFD even when it is, and luggage compartment light never comes on

Ok, my fault missed the post about the MFD display.

 

[rich11235]

No worries

 

[rich11235]

OK helpful people, I've done a bit more investigation. Trying to work out the logic of the microswitch and what it does, a little bit hard without a wiring diagram, but anyway:

Microswitch has three positions: full open (latch jaws open to receive the striker), half latch, full latch
It has 3 pins which are plugged to 3 wires white-brown-white, let's call pins A, B, C

In full latch position, the microswitch does not connect any pins together, so open circuit between A-B, B-C and A-C. This confirms what an earlier poster suggested - its a normally open switch
In half latch position B-C are connected together
In full open position A-B, B-C and A-C are all connected together

On the van body side, bridging wires pins B-C in the plug moves the power latch at the striker plate (the thing that pulls the tailgate in) OUTWARDS. Bridging across any other combination of pins does nothing. And nothing I have done with the plug managed to bring the light on or indicate tailgate open on the MFD.

Is that the behaviour of the switch that is to be expected (anyone got a wiring diagram?) and any ideas where to check next to get my light on and the MFD to show tailgate open?

 

[WelshGas]

OK helpful people, I've done a bit more investigation. Trying to work out the logic of the microswitch and what it does, a little bit hard without a wiring diagram, but anyway:

Microswitch has three positions: full open (latch jaws open to receive the striker), half latch, full latch
It has 3 pins which are plugged to 3 wires white-brown-white, let's call pins A, B, C

In full latch position, the microswitch does not connect any pins together, so open circuit between A-B, B-C and A-C. This confirms what an earlier poster suggested - its a normally open switch
In half latch position B-C are connected together
In full open position A-B, B-C and A-C are all connected together

On the van body side, bridging wires pins B-C in the plug moves the power latch at the striker plate (the thing that pulls the tailgate in) OUTWARDS. Bridging across any other combination of pins does nothing. And nothing I have done with the plug managed to bring the light on or indicate tailgate open on the MFD.

Is that the behaviour of the switch that is to be expected (anyone got a wiring diagram?) and any ideas where to check next to get my light on and the MFD to show tailgate open?

@Loz might be able to help. Unfortunately as you are not a VIP member you can’t PM him.
He might see this message .

 

[rich11235]

Thanks WelshGas, sorry what's the VIP member thing? (new to the forum as you can see)

 

[WelshGas]

Thanks WelshGas, sorry what's the VIP member thing? (new to the forum as you can see)

VIP membership gives you access to the VIP area for Discount Codes and various documents etc in the Resources area.

See here.

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