Britbike forum Forums British Motorcycle specific Brands Norton bulletin board bad ammeter

thanks for your reply , my bike is neg earth and the feed from the reg should go on the neg side of the ammeter as the book says ,when i changed the terminals over so my neg went to the pos side of the ammeter it read discharge as it should but when i started it up it drained the battery right away , perhaps the ammeter is pos earth , or does it matter

May we assume you have a dynamo DC generator?



Can you see how this works?

It’s for a 1957 Dominator, but it must be similar.





Brown, then brown/blue, goes from battery live (-ve on this diagram), to one ammeter terminal.

Regulator brown/white charging wire and all the loads (except horn and brake light) go to the other ammeter terminal. If the ammeter reads backwards, change the wires over to the opposite ammeter terminals. All the ammeter is doing is showing the direction of current- in or out of the battery and how large that current is.

yes Triton, thats pretty much the same as mine , so ammeters are poss and neg and can be wired either way round ? so how can i measure what is coming out of brown and white . to see if its charging

You think it’s not charging? Does the headlight not get brighter when you rev up from idle rpm?

The first test I do is to join dynamo D and F together (isolated from the rest of the wiring) and connect a headlight bulb between that combined D/F and the engine casing. Start the engine. When I rev it up, the bulb should light brightly.

If it doesn’t light, I briefly connect battery live to dynamo F and try again. battery earth side has to be connected to the frame while you do that brief “flash” on F.

If the dynamo lights the bulb at something over 2000 rpm, you have a working dynamo.

Next test is to connect the dynamo to the regulator and try the bulb or a voltmeter between its output (A on the diagram) and the engine casing.

no the head/lamp dont get brighter , i have done the test with the bulb on the dynamo and it lights up strongly its the brown and white wire from the reg to the ammeter i want to test can i use a bulb to earth or a multimeter thanks PP (ive just bought a solid state 6v neg earth )reg

Peter,
If the neg Earth regulator you bought is a Podtronics one, then you should be aware that it requires the dynamo internals to be wired differently than when used with the electro-mechanical (MCR2) regulator.
.. Gregg

hi Gregg , this one is from wassell i just followed the instructions , i cant see the name you said , cheers PP

Peter,
IIRC, the Wassell neg earth regulator is a direct copy of the Podtronics dynamo regulator. (And not nearly as reliable)

Check the installation instructions carefully: given that it is like the Podtronics, one end of the field winding goes to the Dynamo's "D" terminal, and the other goes to the "F" output terminal.
.. Gregg

did the battery discharge
when ammeter was connected
... and the old mechanical regulator still fitted ?

The mechanical regulator has
a spring counter-loaded
solenoid relay-contact
low voltage cut-out
... that normally opens the contacts when
the generated power through the solenoid
Falls below the strength of the cut-outs spring

... this electromechanical solenoid
is what keeps the battery from discharging into the generator
at low to no rpms
... sort of like a mechanical diode

Given the Wassell neg earth unit is like the Podtronics, then it looks to me like the above instructions are not correct, or at least misleading.

The Left hand sketch purports to show the dynamo's standard internal wiring. Such is not the case, because one field lead goes to earth, and the other goes to the "F" terminal. The drawing on the right shows the correct standard wiring.

It looks to me like they have interchanged the titles above the sketches.
.. Gregg

I'm glad someone made some sense of those diagrams.

I looked, and thought I've lost track of how these things are supposed to work !
FADE used to be how it all hooked up, in a std system.

thanks , i have wired the reg by the colours yellow to D, green to F , black to earth , the red wire to the neg side of the ammeter

Do you have a diagram with these colours listed or shown ?

My memory may be a little sketchy with what has gone here before,
so it doesn't hurt keep us and this info up-to-date.

(over the years there have been many such discussions)
(if only all wiring diagrams and add-ons were consistent !)

thanks so does this mean i have to reverse the F and D ? LIKE green to yellow terminal , and yellow to green terminal , thats what the drawing on the left looks like to me

Given that Wassell is the same as the Podtronics (and I'm sure it is), you wire the dynamo internals the way shown in the left hand "Old Configuration" drawing. The Right hand drawing is wrong in that it shows the dynamo's internal wiring for a Positive Earth configuration using a Podtronics or a mechanical regulator.

Convention has it that the regulator's yellow wire goes to the dynamo's "D" terminal, and the green wire goes to the "F".
. Gregg

yes finaly i got in touch with the supplier, the yellow goes to F green goes to F , wich is opposite to how it was , and now it reads a charge on the multimeter the ammeter still dont work , i will get another one , thank you all for your input and patience

I had better let you know , the ammeter a got from India was no good , i bought a genuine Lucas one and everything is ok now , i want to thank all you good folks for helping me . PP

Put all the cables onto one stud, it doesn't matter which one. The ammeter won't be much more inaccurate and it won't plunge you into darkness at the worst possible time

A broken ammeter won’t do that anyway, if power is being generated.

That rather depends on how 'broken' it is, surely ?

If the needle merely doesn't move, then no problemo.
If power doesn't actually still flow through it, then no lights !?

Look at the wiring diagram. The brown & white regulator output (A) is connected to the light switch. Feed to the light switch and regulator A are both attached to the right side (as seen on the diagram) ammeter terminal.

A broken ammeter coil (common problem!) does not isolate the charging system from the lights.

But but but ... does a feeble glow count as 'lights'.

In top gear, you'd have to be doing 30++ mph to have anything like visible light emanating.
Obviously in the lower gears around town it would be lower speeds (similar rpms though).

Reminds me of my little Villiers. With no battery, and only direct ac lighting.
At idle at standstill, glow worms would be more useful !
Any attempt to connect up a stop light robs the lights of ANY chance !

My reply was to this:

In top gear you should be well over 30 mph-- otherwise you are a lugger and I shall report you to the Royal Society for the Prevention of Cruelty to Pistons!