Did you find the problem Wayne? Reason I ask is that my '91 started doing a similar trick. The 40A fuse under the hood is blowing as soon as the light stalk turns on. Not sure if thats the fuse you are reffering to? If not, it must be the 15A one in the fusebox. Im guessing that there must have been some chafing on the last run, now grounding a wire on the chassis. I found my main flasher beams to work as do the popups, so the problem lies on the sidelight circuit I think. Have you tested this? Actually, mine still pops on removing the 15A room fuse so I guess the problem lies under the bonnet rather than with the sidelight/room circuit, maybe around that pesky relay that pops up the headlights on switching on the sidelight, which im still trying to isolate.
Its a process of elimination and any further tips would be helpful to both of us im sure, good luck!
Regards,
Mark