Plus2: tail and panel switch wiring route:

[TonyA]

Hi, the I have a short (to earth) somewhere between the wire that goes to the tail light and to the Panel Switch from fuse #3 (mine is the 3 fusebox in engine bay version). Interestingly it blows the fuse when I engage the Sidelight
Switch when the panel light switch is in the "Instrument Lights Off " and "Neutral " positions, but ok when in the "Roof Lghts On" position . I see from the circuit diagram that there is a" branch (I guess a 1 into 2 bullet connector) somewhere between the firewall and the dash; providing one live to the Panel Switch and the other to the tail light. Does anyone know the path the red tail light/ Panel Switch wire from fuse 3 takes after it goes in a bundle thru the bulkhead and into the interior ..

I forgot to say, I separated this rogue red wire from its pair at fuse #3 that supplies the front sidelight, which is OK ..Thx in anticipation...Tony

[gus]

IIRC that switch provides ground to the interior lamps, but it must switch power to the instruments....
The self holding relay for the side lights is right there, so perhaps the issue is right there.