Still searching ...

... Or the plot thickens! Did a few more checks on 't Kreng in the hope of finding an easy fix and found some interesting things;

The first one is that with the ignition switched ON I get  a reading of approximately 12,5 Volts at the positive terminal of the coil. As the ignition system comes with a built in resistance or ballast wire the current at the coil should be around 6 Volts. A quick check on the DHC proved this point. This should give a rather healthy spark but the coil might suffer in the end.

So next item on the check-list was the coil. With a constant voltage of 12 V it might be damaged. But with readings of 2,3 Ω for the primary winding and 10,8 KΩ  for the secondary winding it doesn't look to bad.  Although according to the work shop manual the primary coil should have a resistance between 1,3 and 1,45 Ω. So will have to find the manufacturers specifications for this coil to see if something is wrong there.

And then there is the question why I do get 12,5 V on the coil? Is there something wrong with the ballast wire or did I make a mistake while rewiring the ignition switch when I installed the central switch panel? Checking the redundant ignition switch, which I removed from the car many years ago, showed me that two wires were cut inside the loom. So easy to miss when rewiring the ignition for the switch panel.

Clearly to be continued as I can't see a definitive solution for the problem yet. But sadly at the moment lacking time to work for a longer time on the car ...