Hi All
Been doing some work on the inst cluster and the TACHO ive drawn out the blue flexi pcb circuit and the connections to the main rear 28 pin plug which may help others..Note if you remove the main pcb from the flexi then it wont work as there is a NEG supply interlock provided by the main pcb you have to link out the 2 pins if you want to work on the flexi blue pcb see drawing
ill be drawing out the tach circuit soon to modify it for seat engine conv as weve done that and only thing is the tacho that needs attention ive plenty of KEFA635 ics to work with will update when i know more.
Updated new tacho circuit diagrams of pcb work in progress
seems VDO chip can control tach calibration settings as vdo chip connects to KAFA config pins
basicly signal comes in via 100k and 6,9k to ground and into TR2 then via 12k into pin 13 other stuff attatched but thats the basic signal path.....