The 928 has a light under the hood that is supposed to light up when the hood is opened. The pre 1990 series have a mercury switch to activate the light.
If the light housing is taken apart you will find a mercury bulb inside and if the ends are cleaned then your light will work again. This assumes that the wire is connected properly to its connection under the cowl cover, and the bulb is good. I believe that the hood switch controls the light operation on cars mfg after 1990.

I was looking into the under hood light that wouldn't.
I removed the plastic cowl under the hood, traced the harness to the connector that had 3 wires going into it, disconnected the connector and turned on the lights. I got power to the car side of the connector so i took the ohm meter and set it on tone and for continuity to the center of the light fixture, no joy for the gray wire.
I removed the light fixture screw, and looked at the light fixture, on one side it has a small tab that's bent in to hold the innards of the light fixture together.

I unbent the tab and the inner contact slides out it has a metal spring and a round plastic contact holder that has 3 small cut on the sides of it, I separated the slides till the contactor pin started to come out , I removed it from the plastic part and out fell a glass tube filled with mercury,

This has a metal wire that's cut at one end, i took the ink (grey eraser) eraser and cleaned both metal ends of this glass tube, also the brass center contact on both sides, I checked for continuity from the bulb side of the harness to the contact and I found continuity, i replaced the glass tube with the cut wire part closest to the wire , reinserted the brass contact part, and slid the plastic back into the bulb holder, inserted the bulb and bent the tab back so to hold things together when the bulbs removed.
Connected the harness back together and now we have lights, car is an 85 32V