I have trawled through a few CCT diagrams for Berlingo's of that era. I can not guarantee my results are accurate but it seems to tee up.
Ok, the cigarette lighter is a red herring. It only works in the 'on' and 'ignition' positions, directly from the ignition switch. There is no permanent power to it.
All the other problems seem to stem from the fact the shunt is missing. It supplies constant power to the BSI and all the other circuits that you mentioned. Some circuits derive switched power from the BSI. Some circuits derive permanent power through the BSI. Some circuits, directly from the shunt.
The only fly in the ointment was the interior lights. But the lights appear to have a switch to select between "permanently on", "off" and "power controlled from the BSI" (I don't know how the switches would actually be labeled. Probably pictograms?). I'm assuming that the lights only work in the "BSI" position? (Does anything work in the 'off' position?
)
The power from the shunt to the BSI would normally supply 60 seconds of "standby" power for things like the interior lights and the dash. As a "courtesy" the interior lights com on when the ignition is turned off. Typically after 60 seconds of the ignition being turned off, the BSI starts shutting power down (including the courtesy lights). I bet when
you turn the ignition off, everything goes black instantly?
The only thing that I can think, is that the previous owner removed the shunt to reduce the load on the battery while the car was waiting to be sold, and they forgot to reinstall it? Have you contacted the previous owner to see if that was the case?
