Outer Limits 4x4 Board

1989 hilux keeps blowing the instrument fuse, noticed just before it would blow the tacho would start jumping around and the radio would cut out then come back on straight away. I suspected it was something to do with the tacho so i opened the cluster to find a fkd capacitor on the tacho pcb replaced that tested all diodes replaced all resistors but still blew fuse. then i basically removed the tacho from the equation by disconnecting it inside the instrument cluster. Still kept blowing fuses. by following the tracks on the back of the cluster the only 3 things supplied from that fuse are fuel gauge, temp gauge and tacho. I disconnected all 3 but still kept blowing fuses. Then i changed the whole instrument cluster over to a diesel one i had, knowing it wouldn't work just wanted to see if it kept blowing the fuse, which it did. tried testing between load side of fuse and ground after the fuse had blown but got nothing.

IT ONLY SEEM TO HAPPEN WHEN DRIVING I.E - MOVEMENT

This is doing my ShortyIQ head in any suggestions would be muchly appreciated

ok after 4 days and about 16 hours i am 99% sure its fixed. disconnected the coolant temp sender and the fuse has stopped blowing, which is strange because according to the wiring diagram i have if i unplug the instrument cluster all the senders have their supply removed. Anyway it seems to be ok now