Substan

RicardoM thanks again for your help when i can i will try again at the conversion and check all contacts areas mentioned, i have reviewed all the history of this project and i have a question perhaps no relationship to tacho but what is the purpose of the door contact as a signal input for the ECU?

Must admit i never saw donor tacho working but is does seem strange that fitting extra component without severing original signal link would give the required waveform putting this in basic terms if water flows through a pipe at constant velocity and i introduced another pipe with variable velocity unless i stemmed the flow of constant velocity i wouldn't see the variable flow at the end of the pipe

RicardoM i carefully drilled and soldered the additional component and still get the initial movement at startup on the rev counter is there something i have missed as im thinking i need to remove the original sinusoidal signal to allow the new square wave or as i see from your explanation diagram can i just simply splice yellow green input signal wire and solder the HCF4040B pin 10 and 9 as shown or is this too simple my knowledge of electronics are basic but i am an experienced mechanical engineer, i have enjoyed this little project and hope it has aided other members of the group, no harm done if it doesnt work maybe i should look out for a diesel instrument cluster with fitted tacho

Please advise on conversion and im interested in your explanation why a zener diode is partially correct but will not work

Sorry not thyristor rather 5v zenor diode, i should never try having a conversation whilst writing

Appreciate getting back as for donor clock im not too sure but believe its from a 1.3 petrol, i understood from your forums that a petrol version uses a 5 volt signal input so i have fitted a 5 volt thyristor in line with the yellow/green signal wire however the tachometer still fails to operate but i have noticed movement on starting, is this due to the battery voltage reduction on initial start? I have also changed over the fuel and temperature gauges as suggested and these both work correctly

I too have a 1.9 diesel pickup and im interested in converting a 1.3 petrol tacho to use on my diesel engine, if the conversion is possible please advise and finish your forum post, many thanks for accepting me as a member