1982 VW Westfalia Restoration

I'm hoping one of the fine mailing list members might offer guidance on
the wiring loam under the sink.
Images of the wires in question can be viewed @

http://zzyzx.org/1982poptopsaratoga/images/interior/camper_wiring/Cabinet_wiring.html

Green is connected to water tank level
Yellow is connected to positive at the water pump
Red & white are connected to the two power wires from under the drivers
seat which are also red and white in this camper

That leaves the two black wires.
Does one go to the negative at the pump.
Where do the other black wire run?
Would it go to ground at the body number 6 point along with the water
tank black wire?

Here's a photo journal of the progress for those with interest.
    http://zzyzx.org/1982poptopsaratoga/index.html
It was a shell loaded with the camper equipment.

Also, a question about the list.
When I send an email to the list it doesn't show up in the list thread
that I down load...I wonder why?

TIA
Steve