[kwilford]

Before you become one of those dreaded "PO's" (Previous Owners) yourself, you need two items BEFORE you start "fixing" electrical wiring.

1) A wiring diagram, which is available on this site, or in pretty much any decent service manual. IMHO, the best are in the Opel Factory Service Manuals, which has a complete diagram (a bit confusing to follow) and individual "system" diagrams (which have far fewer lines to follow and focuses in on the problem you are having). The Destec wiring diagram is also pretty nice (I have Revision M), but can be a bit daunting to a beginner.

2) A test light. A simple lighted probe, with an alligator clip to connect to ground, and a pointed end that when touched to an energized wire or contact, causing the probe to light up. You use this to find out what is energized, and where the power is coming from by disconnecting the apparent source and seeing if it is still energized.

It is really difficult to try to diagnose electrical problems over the Internet. I "think" that what you have is a toggle switch that is providing power that actuates the relay. Terminal 85 normally has the yellow wire with a black stripe that actuates the relay from the headlight microswitches. I think your toggle switch merely has replaced that function, so that is fine, as it seems the microswitches aren't working. But if the toggle switch gets its power directly from the fuse box, you need to find out what the parking light switch is providing power to. If the relay is supplied through the parking light switch, then a melt down is in your future.

To further explain, the relay is itself just a switch. The "supply" comes from the fuse bus (the big red wire) connected to terminal 30/51. Inside the relay is a set of contacts, which are normally open. When power is supplied to terminal 85, a magnet inside the relay pulls the contacts closed. This then connects terminal 30/51 to all four terminals marked 87. Three of these are running lights, instrument lights and license plate lights, which can also be powered separately from the parking light switch. The fourth supplies power to the headlights through the white wire with the yellow stripe (via the adjacent dimmer relay), which is a big load. Lots of current. If the parking light switch is somehow in the middle of the supply line to the headlights (at either side of the relay), it isn't designed to handle the current that the headlights need, and will melt down.

HTH