I am having a similar problem, well actually haven't had any problems til last night. Have a 70 240Z hadn't driven it for about a month cause it is so blasted hot in Arizona. The instrument cluster and tail and side lights blew when headlights were turned on driving home last night. When I got home I checked the fuse and it had indeed blown, replaced the fuse and the lights went on and off just fine--then I started the engine and turned on the headllights and zap it blew the fuse--did it twice cause I am stupid. I have a brand new headlight combo switch put on a couple of years ago and also have the Motorsport fuse box. What could be causing it to blow the fuse with the engine started and not with it off? Ward Fogelsanger