I was handed this by it's auther, Bob Sullivan, at the GMC Classics Rally in Uvalde, Texas in October of 1999. I hope you find it useful.

Many people would like to have the convenience of a water pump switch in their bathroom. The following is my solution for a 1978 Eleganza and other similar models.

Referring to the diagrams below, please note that the light in the original pump switch (L1) is contained within the switch (SW-1). The light for the new switch being added to the bathroom (L2) may also be contained inside the new switch (SW-2), if you can locate a switch that is so configured. However, if you do find one, make sure that such a switch has separate terminals for wiring the light, otherwise I suggest using a separate light.

The original GM panel switch that is located on the Switch Panel by the front door in the Eleganza may be used; but, if it is used, it must be modified (see below).

If you opt to install two new switches, SW-1 and SW2 (both SPDT) can be any type of switch (toggle, rocker or slide), but they must have a minimum rating of 5 amps. L1 and L2 must be 12 volts.