Morris Minor Owners Club

Chasing an electrical fault that turned out to be a bad earth I’ve messed up the regulator, or dynamo or both.

So, I have a voltmeter fitted which fluctuates between 12.4 and 17.7v when driving. Steady 12.7v at idle. When the voltage drops the ignition glows brightly but the car drives fine then for no obvious reason the light goes out, voltage increases and off we go again.

So have I knackered the dynamo or regulator. Do I need to adjust (again) the regulator (not too sure yet how to do that correctly)

Should I just hasten the conversion to alternator and be done with it?

The dynamo can produce higher voltage than required, depending on speed. As it can make 17V, it is OK. However, your battery will not last long if charged at 17V! That is why a regulator is required between the dynamo and battery.

It might appear that something is wrong with the regulator. Either the actual regulator or the wiring.

How could you have messed up the regulator or dynamo? The most likely issue is a bad connection or dirty contacts in the regulator. The fact the ignition light goes out "for no obvious reason" suggests a bad electrical contact.

Check the electrical connections at the back of the dynamo are clean and tight. Then check the connections at the regulator end at "F" (field) and "D" dynamo. Open the regulator box and you will see two bobbins which have contacts ("points") at the top. With a piece of fine emery paper inserted in between the contacts, carefully clean the points. If you double the paper over you can clean both points at once. If the paper won't fit doubled over, use one side and turn the paper over. Now try running the engine.

When you say adjust (again) the regulator does that mean you have fiddled with its settings?

Don't panic! It's probably something easy.

Stephen

Yes, I should have made that clearer.

In an effort to trace a different issue I adjusted both screws on the regulator. This had no effect as it turned out to be an earthing issue but in the process I ‘lost’ the original regulator settings. My attempts at re-finding the original settings haven’t gone well as I now get the fluctuating readings and sporadic ignition light. It’s the light that makes me wonder if I’ve overcooked something.

The manual says to adjust with a moving coil meter which I don’t possess. (Just 3 dvms which lack the latency of mc)