In building a wiring harness for a stock 914-6 I've discovered there's an extra wire from the relay board in the engine bay that goes to the gauges, but is not used in a stock 914-6. Art Zapf's wiring diagram shows the wire, but lists it as "for sporto". The wire is green and connects to terminal #4 at the front of the relay panel in the engine bay, and is just hanging there not plugged to anything with the gauge wires, behind the gauge panel.

A 914-6 has a oil temp gauge and a warning light, no oil pressure gauge. Most guys add an extra wire if you want to upgrade gauges to include a pressure gauge and keep the warning light.

Terminal #13 on the engine harness (rear plug terminal)isn't used. However that terminal on the relay board passes right through to terminal #4 at the front of the board, where the mysterious green wire is connected.

So if you have a real 6 and want the add a gauge, the wire is there for you!

Very good sleuthing!

very nice ....I have Arts diagram as well !blowed up by 4 times the size ..makes for easer reading

In the "For What It's Worth" file, here's a picture of the mysterious green wire behind the gauges. In a stock 914-6 it's not connected to anything at the dash or gauges.