Instrumentation fuse repeatedly fails

[nev]

I have a problem with my 2010 Berlingo First 600 HDi (variant GB9HWC, version EURO4G*9HW*).

Internal fuse #15 (15 amp) intermittently blows. It appears to only do this between the engine being turned off and the next time the key is turned in the ignition. It does not happen while the engine is running. It can go through a week of daily use before it occurs again.

As far as I know, that fuse is responsible for "instrument panel, radio, screen VAN network". (I have no idea what "screen VAN network" is).

When the fuse is blown, I have disconnected all instrumentation and radio and rigged up a headlight bulb in place of that fuse. That bulb lights, indicating to me that there is still a problem and that it is an earth fault I have checked and pulled on all the wiring that I can access between that fuse and the instrumentation terminals, but my check light remains lit.

Similarly, when the problem fixes itself overnight, I cannot induce the fault through moving the wiring that I can access. Instead, I replace F15 and everything works fine for a few days.

A few questions:

1. What is the "screen VAN network"?

2. Does anyone have a wiring diagram for this so that I can follow the relevant wires individually?

3. If this is an earth fault, am I wrong in assuming it would be between the fuse and the instrumentation terminals?

4. What have I overlooked?

Thank you.

[nev]

To my surprise, I have actually made some progress with this fault...

At the moment, closing the sliding door causes the fault. Opening it again alleviates it.

Leaving the sliding door open and closing any other door brings the fault on again. Similarly, opening that door alleviates it.

Presumeably, this link between the door sensors and the electronics is goverened by the "screen VAN network". Do the symptoms that I have listed make it more likely that something central is causing the ground fault, or could a fault in the wiring to any one of the door sensors be causing it?

If it is something central, then where should I be looking? Or, to rephrase, what is the "screen VAN network"?

[Sol]

Vehicle Area Network is what VAN means. It's the early version of a serial communication network between every device in the vehicle. Now called CANBUS.

Using a pair of twisted wires, white and red or cream colour for example, visibly twisted together. Those are the wires for communication. Any damage or disconnection will cause very weird issues. You will have to inspect the wiring in that door lock as it is used to signal the BSI that the door is closed or open, used for locking & interior lighting control of course. Each lock has its own controller built in to communicate with the BSI.

Each end of the VAN bus has a 120R termination resistance, so the resistance across any pair will read 60R from the parallel value. Anything else shows a fault and you can lose all devices after the damaged or disconnected section, also the entire network can shut down and nothing will work.

F15 is for control panel and display screen but a short on the wiring in the door umbilical section will cause havoc and blow that fuse if it's part of the VAN+ section.

[nev]

Thank you Zion, that is exceedingly helpful - if a little daunting!

It sounds from your description like a problem in any of the VAN wiring (not just that for the doors) could cause the fault. Is that the case?

Where are the ends of the VAN bus? Presumeably one is in the BSI?

[Sol]

It's hard to say, but yes the start will be at the BSI and the end is on the last device on the chain (not well documented unfortunately). If you can replicate the error with the side door open then it's worth starting there. Look for any obviously twisted wires, those are always comms wiring, Vanbus or Canbus and always look the same. Twisted all along the entire length, they really stand out.

I'd think the issue would be in the rubber guide tube between the door and the body, peel that back and look for split or cracked wiring first, it could be easy to fix even if it's hard to locate. Wiring issues usually are that way round.

[nev]

I believe that is solved now, thank you!

I found a wire in the stantion behind the sliding door (a wire leading to that door) that was definitely grounding with the vehicle body.

Cheers!

[Sol]

Excellent! Glad to be of help.