With the second electronic regulator not seeming to work either it’s time to turn to old school tech. I borrowed the regulator from another Bella waiting for restoration:

It took a few hours to get rid of completely rusted stuck screws, but the regulator cleaned up quite nicely.

The insides were not bad at all either:

Not fully o.k. though; the 12V coil was not making contact when depressing the top of the regulator:

To fix this I needed to unscrew the regulator and loosen the screw pointed 1 from the bottom of the aluminum. That allows the spring with the contact to be pushed slightly to the left (see arrow 2). This brought the points back into contact when the top is depressed by hand.

When the engine is running the coil will pull the top down through generating an electromagnetic field.

The other points that should be doing the regulating I wasn’t sure about so I left them alone.

Next I installed the regulator in the Bella. Before testing the regulator I of course had to re-connect the resistor in the Dynastart.

This is key – do not forget to do this.

Four hours of work later and…. exactly the same symptoms as before… The good thing about a mechanical regulator though is that you can observe it working. So next was an experiment; I created longer cables so I could have the regulator on my workbench rather that built into the Bella. A bit of soldering later this was ready.

Starting the Bella showed the following:

• The 12 Volt cut-off switch (to stop back-flow current) is working fine. At low idle the switch is open and at fast idle the switch closes; this means that when the voltage is high enough (>13V) the contact closes to let current flow into the battery to charge it.
• The Other contact stays closed at low idle and starts to spark at high idle. It doesn’t however touch the other contact nor does the voltage stay under 14 or 15 volt:

I made a quick movie of what the contact looks like in action:

If you look carefully you can see that the contact sparks and does not move over to the left contact (try full-screen).

Here’s the movie to download in MKV (it is better in MP4):

Sparks at the contact

Time to contact the specialists on this; I’m out of ideas…