A Type

Disconnect the wires from the dynamo.

Connect a voltmeter. one lead to D, the other to chassis (range dc 20 v)

Start the engine, but keep it down in fast idle.

Checking the remanence

It should be possible to measure a voltage of 1 to 2 volts, this is due to the residual magnetism left in the dynamo. Without the remanence, the dynamo will not be able to start.  



The remanence can be lost by prolonged inactivity, or if the dynamo has been separated for renovation.

You can magnetize the dynamo by connecting D to the battery for a second or two, eventually connect F two chassis.


Testing the dynamo

With the engine at high idle, connect F to chassis with a piece of wire, voltage should show 6 - 10 volt (it can get much higher, depending of revs.

This should not be exaggerated, the dynamo is unregulated and can be damaged. If only measuring 1 -2 volt, the field coil may be interrupted.

A 12 V bulb can be used instead of the voltmeter, but it is first to be connected when the F to chassis connection has been established, and the engine started. The initial power is so weak that the bulb would "eat" it, and prevent the dynamo from starting.

The motor method

Dynamo dismounted

This method is not entirely safe, but give a indication of whether the dynamo works.

Connect F to chassis with a piece of wire. Connect D to the battery. Other side of battery to be connected to dynamo chassis.

Remember to to use the correct polarity, + or - to chassis.

The dynamo should run like an electromotor, and in the direction it is normally pulled. Change of direction is done by switching the wires for the field coil.

I above is OK. you should show interest for the wiring and the control box.


Checking the control box

With the dynamo mounted and the wiring connected, and a fully charged battery. Connect a voltmeter, range 20 V dc, one lead to A, the other to F.


You should measure something like:

0 - 1,5 V at idle, going up to

5 - 6 V at high idle, for then to fall to 

1,5 - 2 V at high  revs.