Does the harness include a relay? It should be a fairly simple circuit:
- Fused hot wire from battery to pin 30 on relay (I usually just use an in-line fuse)
- Switched 12v (or unswitched, if you want to use lights with key off) to dash switch
- Other side of dash switch to pin 85 on relay
-...
That switch should work, but without knowing where these new wires lead, it's hard to say where the problem might be. However, here are a couple of things to consider:
- The white/black should be your ground wire. I see you're using a red wire on that pin. Red often means "hot." Anyway that pin...