Cargo bay light always on and doors wont lock

[Bill H]

Mk7 Transit and the interior light in cargo bay is permanently ON.
So it thinks that either the side door or rear door is open and wont lock the van (horn beeps), I thought it was the little plunger switch on side door so I unplugged it but made no difference.
Im assuming that the switch is normally closed so that when the door is open it switches a wire to ground, so unplugging should turn the light out - can anyone confirm if thats correct please?
Ive pulled out wiring loom to side door but can find nothing wrong.
Is the interior light on a relay - if so which one and where is it?
Is the back door ajar switch part of the lock mechanism?

Help and advice appreciated as always

[Altransit]

The load space lights are controlled by the BCM, there are no relays, so in any case they will be switched off after 20-30 minutes even if the doors are still open.

If you've checked out and eliminated the sliding door switch, and contacts, then the problem is probably within the rear door loom, where it flexes in and out of the opening rear door.

It could also be an actuator not working properly.

[Bill H]

The load space lights are controlled by the BCM, there are no relays, so in any case they will be switched off after 20-30 minutes even if the doors are still open.

If you've checked out and eliminated the sliding door switch, and contacts, then the problem is probably within the rear door loom, where it flexes in and out of the opening rear door.

It could also be an actuator not working properly.

Thanks for that Altransit, I must admit that I didnt wait 30mins to see if they went off.
I thought that the fault was with the little switch on the sliding door, when I gave it a good workout the lights went off and the alarm set OK, so I took the switch out to have a look and see if there was an obvious problem - and now the fault is solid whether I leave the wires to it shorted or open. I pulled all the wiring loom out as far as the headlining in the cab and all looks perfect - perhaps theres more to the switch than I thought a resistor inside perhaps so the BCM knows if its disconnected?
I think I'll start with a new switch and pull the loom out for the rear door.

[Bill H]

I was going to put a meter on the Central Junction Box (CJB) to see which switch was the problem it looks like connector C2 at the CJB is where all the wires come back to.
ANyone know where the CJB is - and which is connector C2?

[Bill H]

Update and FIX.
After a lot of red herrings - finally fixed, it was a broken earth wire in the rear door, I'll put all the details and pin outs below as Im sure this is a common problem.
Every time I touched something the fault would go away for a while just to keep you confused.

I looked at the central JB (the hidden one behind the glove box, located connector C3 (top left BLACK 2nd one down) theres actually 2 connectors in the locking housing so to get to the pins I had to slide the connectors out the housing.
Looking from the wiring side of the bottom connector the pins number 1-10 from left to right then next row up 11-20 left to right.
C3-19 Green wire is +12v when the passenger side sliding door is CLOSED
C3-14 Green/violet wire is GND when passenger door is CLOSED
C3-1 White wire is GND when driver door is CLOSED
C3-13 Yellow/Orange wire is GND when rear door is CLOSED

C3-13 didnt switch, I never saw an earth.
The rear door switch is inside the lock mechanism, pin numbers are visible on the connector, at the rear latch connector pin 8 the yellow/orange wire goes to the switch and switches to the Black/Green wire on pin 6 - this wire should go to GND but I had an open circuit. Pushed a pin through the black/green wire and jumpered to GND - hey presto alarm works and cargo bay light switches off after 30secs.
Was going to put a new wire through the tube that holds the wires around the hinge but as I cut back the insulation spotted the broken wire - resoldered and all OK.

[Altransit]

Excellent bit of diagnosis, good result