About a year ago I bought a 1960 basket case. I've come a long way, and have the engine running.
As far as I can tell, it's a 425, with a 6 volt system.
With the engine running above idle, I power up the field, and the dynamo lead puts out more than 6 volts, but it's in the wrong direction. I have an analog meter, and the needle goes to the left. When I reverse the meter leads, it shows up to 8 volts in the correct direction.
Very perplexing.
David

The dynamo needs repolarising ( and your meter needs recalibrating ).

Here's how that works with a Lucas dynamo, if you're not sure about the one on your car, some more internet searching may be in order...

http://www.dynamoregulatorconversions.c ... dynamo.php

I tried that to no effect. I flashed the field with the 6v side of the battery.
I'm going to pull off the fan and take a look at the dynamo tomorrow. Could I have possibly wired the brushes to the wrong terminals when I replaced them and cleaned out in there? would that explain things?

Has this dynamo ever worked correctly i.e. before you changed the brushes and cleaned it up ?

Does it work correctly when you connect it up with the opposite polarity (swap the -Ve and +Ve over), is the ammeter showing an increase when you rev the engine?

show us a picture of your dynamo please. Do you have the right regulator with the dynamo?

It's morning here, and I'm going to try something else today.
As to reversing the leads, yes, I reversed them on the meter, and got the correct direction.
This is the first time the engine's been run since I bought it. I don't know how long it's been since the dynamo has worked.
I even reversed polarity at the battery, and got the same result.
In staring at the diagrams all evening, it occurred to me that the field gets its power from the armature terminal. The field lead is where it gets grounded through the regulator.
I'm going to see what happens when I ground the field lead today. It's about the only thing I haven't tried.
If it works then, it seems to point to a bad or incorrect regulator.
David

Tried every possible combination. Reversed field leads, and got nothing.
I have continuity through the field coils, and no short to ground.
I have continuity on the commutator, and no short to ground.
I have continuity from the armature brush, through the armature, out the other brush to ground.
I have continuity through the wires to the regulator.
I have 6v at the batt terminal of the regulator.
The dynamo is marked: Ducellier 7276 G - 6V
The regulator is marked: Ducellier 8325B 6V 24A

I see a future of short trips without using lights, and recharging every night.
David

Here is a link to pix of the dynamo. There is a dynamo album, and two sub-albums.
http://s1305.photobucket.com/user/HClew ... t=3&page=0

How long has this engine/dynamo not run? The dynamo poles could be de-magnatised after long not being used. So it will not generate much power this way. It can easy be re-magnatised with the help of a head-light bulb. I will look up the way how to do this.

I have "flashed the field", to no avail. I haven't heard of the headlight bulb method.
Tomorrow I will flash it again with wires directly from the battery to the field terminals.
Does it matter which way the coils are magnetized? Battery positive to either end of the coil windings? other end to ground.
David

Errr,
isn't that the whole point of repolarising?
There are only two choices and at the moment, its polarity is incorrect, so needs swapping.

From that link I posted earlier.

"To polarize a Lucas dynamo for NEGATIVE earth. (shunt field)
Your battery's NEGATIVE terminal should be connected to the chassis or frame."

For a positive earth setup, the battery's positive terminal should be connected to earth.