Morris Minor Owners Club

One for the clever people. It relates to an early car but it has been updated many years ago to the spade type Lucas regulator box in place of the screw terminal one.

What voltage should I find on the small wire to the dynamo?
If I only find a couple of volts (even with the wire open circuit), does it mean the regulator box has developed a fault?


I was working on the car last week, and accidentally started it on full throttle reaching very high revs from key-on. Since then the red light has been shining brightly. My best guess so far is that something got upset in the regulator box and it now does not feed the dynamo via the small wire.
I have checked the other terminals / wires and they seem ok (most are at 12V, checked with a bulb and a meter). I presume the black wires from the right hand terminal are an earth.

Hi
2 tests that might help you to check operation of dynamo and regulator box
1. Armature test
With the main dynamo output lead D (thick wire) removed from the regulator box, run up the engine to about 1500 RPM (twice tick-over speed say) The voltage from the D lead to earth should be between 1.5 and 3.0v, due to the field residual magnetism. If the reading is zero, or much lower that 1.5v, then either the lead or the dynamo circuit is faulty.

2. Dynamo Field Circuit
Disconnect the D & F (thin wire) leads at the dynamo end. Connect an ammeter between D & F terminals on the dynamo, and a voltmeter from D to earth. Run up the engine until the voltmeter reads 12v when the field current should be in the order of 2-2.5 amps. If outside these ranges change the dynamo.

When I get a minute I will post some tests for your RB106 Regulator.
Cheers
Ty