bsi causing power drain

[jasper3055]

I have a problem with a Boxer which has a parasitic drain that is sufficient to put my multimeter off the 10A setting. It can light a small bulb and when reattaching the earth sparks can be seen.
I have traced it to the circuits controlled through the BSI module. When I remove the set of wires that exit the back of this module the drain disappears. The only way I can stop the drain is to isolate the battery or remove the main feed into the drivers side fuse box.
Another symptom of this is that the starter cranks over slowly making the engine hard to start.
The starter is good and so is the alternator. Both feeds have been isolated but the drain is still present.
The Boxer has been converted into a camper and I can only think that someone has taken a wire from one of the BSI circuits but have taken it before the fuse rather than after it so the fuse cannot blow
Any suggestions would be appreciated

[moizeau]

Welcome, Have you got a 2nd battery with or without a split charge relay?

[Peter.N.]

For a heavy drain the most likely culprit is the alternator, it maybe charging OK but it can still have a leaky rectifier/regulator. Disconnect the lead and put the ammeter in series with it, shouldn't really read anything. Sorry just noticed you have all ready isolated the alternator so the only thing you can do is isolate one circuit at a time until you find the offending one.

Does it have an auxiliary battery to power the conversion? if so you have presumably tried disconnecting that. It could be that something is keeping the BSI running but the power must be going somewhere with a good heat sink or you would see or smell smoke somewhere.

I had an early C5 some years ago with similar symptoms although it would take a couple of days to run the battery down, that was caused by someone fitting a non standard radio, a Blaupunkt I think it was, all the connectors were the same but it was continually causing the BSI to start up again after shutdown, a different radio cured the problem.

Peter

[jasper3055]

The van does have a split charge system however when the leisure battery is completely removed from the system there is still a massive drain on the vehicle system. I am at present thinking that someone at some time has used one of the circuits controlled by the BSI e.g central locking to take a feed from this circuit to supply power to the leisure circuits- but I don't know. If they have done this then they would have had to take the feed before it passed through the fuse otherwise the fuse would blow or I would have seen it when I checked for a parasitic drain on that circuit.
I am going to check the relay on the heater plug circuit tomorrow if I can find it!

[moizeau]

Have you got a secondary leisure fuse box? If not you should have an 'odd' quite heavy wire (possibly directly spliced into the battery +ve loom) and this should have an in-line fuse.
We are sort of presuming it is the camper circuit at fault though. Have you tried pulling fuses one by one to see if that narrows it down? This will at least confirm whether the drain is pre or post the standard fuse box.

[jasper3055]

The van has got a secondary fuse box which is fed from a fused cable from the van battery.
I have tried the pulling fuses to find the drain source and the only time it goes off is when I remove the main feed that goes into the drivers side fuse box. Removing the wires clusters that are attached to this have no effect on the drain except for the cluster at the back of the BSI unit which keads me to think that somewhere in the BSI circuits lies the fault ,

[moizeau]

So removing the feed from the in car fuse box (at the fuse box?) removes the drain? If pulling each in car fuse box fuse doesn't remove the drain then there must be a non standard splice within the fuse box i.e. someone's nicked a 12v live from within the fuse box prior to it feeding the fuses.

[jasper3055]

That is the idea I have been working on but if they took a feed off the circuit which must be in the BSI system then it must on the feed side of the fuse otherwise when I pull the fuse the drain would go off. I am going to have a look at the central locking , 12v socket, electric windows to start with as these I believe are all part of the BSI control and have a hefty current.
Failing that a box of matches will cure it once and for all!

[jasper3055]

An update . Removed the main feed from the battery into the engine compartment fuse box and the drain is still there - these circuits being fed from this fuse box are not the problem. Also removed the heater plug relay and again no effect on the drain.
So next step seat belt restrainers/air bag system and central locking motors?