[John Stanley]

Motoring does not always mean it will generate, but almost always.  When you motored the dynamo, what polarity did you use.  If you are negative ground,, you should be sure to motor it with negative ground, as this will polarise the dynamo.  Being polarized is important because there must be a small amount of residual magnetism in the field shoe so that enough poser can be generated to close the relay in the regulator that will send battery power to the field.  Unfortunately if the dynamo is polarized in the wrong direction, it starts generating in the wrong direction and will not operate the regulator relay switch.  When you motor it always watch to be sure it motors in the same direction it will turn when charging.

Another test is to disconnect connedtions to the dynamo,  connect F and A together and run a lead to a 12 volt bulb.  Start engine and see if bulb will light up.  It should start out dim but brighten up with higher RPM.  What you are doing here is bypassing the regulator, and as dynamo starts up on its residual magnetisim and starts to produce power, much of that power feeds back to the field increasing output.  If you can get a pretty good light you probably need a regulator.  The reason to use a 12 volt bulb, is that the unregulated dynamo voltage will increase quickly and burn out a 6 volt bulb, and it takes a lot of RPM to blow a 12V, but it can also be done.

re-polarizing is easy at any time, just take a lead from the non grounded side of your batter and touch it to the F connection for maybe 2 seconds.

I always fit V-Reg II electronic regulators, which I fit in the lucas and miller boxes.

[max]

:?

well I am now perplexed. The Dynamo "motors" freely when attached to a battery source with both F & D poles connected in unison, only for the ammeter to show no charge once dynamo is fitted back on the bike, only showing a discharge once the lights are on etc. Do I have a faulty field coil, or does the voltage regulator need replacing (I'm still holding out with the mechanical type at present).

Any thoughts?

[max]

Well after a bit of a fiddle with the dynamo, and after substituting the armature for a spare one, it now motors freely! Thanks again, saved a few penny's there!. I now need to check the voltage regulator as it is also suspect, no charge showing at the ammeter.

[max]

Thanks, will give it a go this weekend

[phutton]

The classic method of checking the dynamo, if you don't have proper equipment, is the motor test. Basically, you connect the dynamo as if it was a motor and see if it goes round.

You can check the armature by connecting the F and D leads on the dynamo with a length of wire, then connect a battery with earth to the dynamo. With a length of wire connected to the battery live terminal, touch either the F or D terminals. The armature should then turn.

To check the field coils, connect the dynamo to earth, then connect the live erminal of the battery via a voltmeter, to the F terminal. A reading here will tell you if the Field coils are OK. If you don't have a voltmeter, just touch the live wire to F and you should get a spark.

Obviously, it is all a lot easier if the dynamo is off the bike.

[max]

Hi,

Can anyone help me ascertain if my Lucas Dynamo requires an overhaul on my model 9. It has been stripped by myself, slip ring cleaned and new brushes fitted to no avail. It's as dead as a dodo. Can I check it's output? Additionally the voltage regulator is the old mechanical type, would I be better fitting a modern solid state type, as I don't know if this too is working?

Jim