right thats the earth on the fan switch when ingnishion is on
to a 3 pin switch
then your goner need a earth and a ingnishion live to the switch

let us know if your going to put a led on your dash clocks and i will help more i wired my 30 amp switch to the spare heater plug light and it also will come on when the fan switch kicks in
on a side note if you use a cheep low amp 3 pin switch it will burn out if you dont use a relay