Coding plug headaches

[Misko78]

Since you have the clock, you do not need one. Coding plug is for engine speed translation for the tach and mpg gauge.

Again I'm sorry for another resurrection.

I have E30 316i M40, previous owner installed old type VDO board which had green line tacho (Alpina maybe?) with coding plug behing it (it has 04 on it), he traded original cluster for it. It gave me nothing but troubles, tacho worked well, but i had brake warning blinking all the time, right turn light sometimes worked sometimes not, handbrake light also, jumping fuel and temperature gauges...

My mechanic gave me for free, like new, Motometer cluster with clock, he could not remember from which car it was. It has a BMW 18 (1 385 364) coding plug. I bought new Sanyo lithium batteries, replaced them, drove like that for few weeks, everything was working like charm. But I wanted tacho so bad, and i bought beaten Motometer cluster, so i salvaged from it tacho with econometer, SI board and coding plug BMW 22 (1 394 110).

I switched clock with tacho, and it was dead, even when i switched coding plugs. I checked SI boards and boards were different. One from clock cluster is missing two chips, dozen of resistors and one capacitor, those components where not installed by factory, nobody did a work on it. So I switched SI boards (again bought new lithiums) and now tacho+econometer works perfectly fine.

All of that got me into repair an old VDO and i changed NiCd batteries and retraced broken traces, someone did a "blow torch" job on it, and also cluster board was full of broken solder points. Now that cluster is fully operational and now i have a spare.

Finally the questions:

1. Which coding plug should i use 18 or 22?
2. Can tacho be used with SI board that has missing components. ( I want to give it to my friend but he also would like to have a tacho).