ok, well this is more information for any one else that ends up blowing this fuse and trying to trouble shoot it. My fuse would blow after the park lights were on for 2 seconds and just about straight away when headlights turned on. This did allow me to observe I had lights and tail lights but still wasn't confident to say they weren't part of the problem. as stated in other posts this fuse blows when there is a problem on the illumination circuit. You loose external front/back lights (except high beam - that remains) and internal lights. First step was to replace the fuse with a NARVA 10A CIRCUIT BREAKER which has a button on it that pops out when it shorts. FSM References: EL-25 - shows pinout for instrument switch EL-28 - shows headlamp schematic EL-30 - more headlamp EL-33 - exterior lamps - clearance, license, tail and stop lamps wiring EL-38 - interior lamp EL-39 - illuminated entry EL-40 - Interior Lamps EL-56 - time control system Not sure all of them are relevant, I referenced anything that had the Lighting Switch on it. Ok moving on, I isolated the front lights by pulling the relays and any fuses i thought might be relevant: Remove H/Lamp RH Relay Remove H/Lamp LH Relay Remove H/Lamp Dim Remove FOG Lamp Remove H/Lamp RH Fuse Remove H/Lamp LH Fuse Remove Stop Lamp Fuse then isolated the tail end by disconnect plugs to number plate lights disconnect driver black box for tail lights disconnect driver tail lights disconnect passenger tail lights now internal: remove instrument cluster wiper pod left the light switch connected on that pod but removed the rest of the plugs. this still powers your cluster though hence removal of cluster plugs by this stage I was a little concerned so looked further at the diagrams and noted some potential in the centre console so next I removed my radio. This fixed the problem, then I added the radio and the problem was still fixed. Now the wiring for this radio was a mess and involved one of the ISO plugs with about 20 wires spliced into a two hacked up connectors. At this stage I decided to get my favourite auto electrician involved to tidy the wires up and hopefully explain where the fault was. Conclusion - bad assumption on my part when I wired the radio up 4 months ago. My Assumption was, a wire can only be one of the following: a) a ground b) if not grounded then it must have power at some stage So when I installed my radio I used a multi-meter to find a ground for the park brake input. Turns out there is a third possibility for a wire: a) a ground that can become active - I didn't ask for more info at the time, wish I had but presumably this applies to the lighting circuit or part of it at least. Maybe some one on here can expand this but presumably some parts of the circuit are double grounded when the light switch is in the off position maybe, not sure... any way, long winded but hopefully helps some one in the future. enjoy.
