Hmmm, I mean soloing the normal but still having it applied as a normal to the preview mesh. This is what I get when I hit 4, not sure what this is, thought it was an error at first so I restarted and tried a different texture and got a similar thing. My workflow usually consists of creating a height-map style B&W image…
My bad, the key for viewing the normal map is 5. However it sounds like you just want to remove the current diffuse texture. You can do that via the 3do custom loader found on the suite bar options.