I know this is an old thread but I thought a reply here might be better than a new thread on essentially the same subject?

My 1.8d van does not have an ECU. It has the later clocks with the digital inset panel. I have purchased diesel digital panel clocks and fitted them, routing the black and white wire from the clocks to the W connector (if memory serves) on the alternator. With the engine started the tacho needle goes to 6k at idle and up (only by 1k as it runs out of dial) when revved. I have bought three sets of clocks now, every seller assured me that they came from a diesel Escort and they all do the same.

Any advice as to how to get this working 'properly' please?

My understanding is that the clocks read pulses generated by the alternator. I tried adding resistors inline with the tacho feed (I had some left over from an aftermarket bike indicator install) but they made no difference. Therefore it must be either modify the alternator (can the pulses be slowed?) or the clocks (can they be 're-calibrated'?)