Ammeter wiring on a A7

[groily]

Swarfy's likely right here, but I would fully charge the battery using a charger first off. Then see what the ammeter says. Just to be sure.  An amp or so would be good to see. A shedload would not be.
Because it is possible for even a DVR2 to die and if by some mischance there is a problem, you don't want to fry the dynamo  . . . .

You could also run the machine with the battery disconnected, measure the voltage off A from tickover, through cut-in and on up to moderate rpm to see if it's stable. As in not more than (an admittedly spiky) 14.5 ish. All well and good if that's roughly what you see. But - if it doesn't stabilise  . . . . then you're not regulating.

[BSA500]

Strangely hoping for a duff battery . Sounds like some good suggestions to try there thanks

[BSA500]

Update-Rode the bike Friday approx 30 miles with the ammeter off the scale etc. Battery voltage has not got above 12.15 volts so I suspect the battery is not a happy bunny. So bought another one( £10 from halfords) in the process off putting a good charge across it

[BSA500]

New battery and meter across the battery reading keeps going up 15 + volts before I chickened out

[groily]

Is the ammeter still showing a ridiculous charge, or have things settled to an amp or so regardless of what you switch on?
What voltage did you see from A to earth with the battery out of play, at 'open road' rpm?
 If you aren't regulating at all, you WILL cook the dynamo, and mess up the new battery as well, so you were right to chicken out for the moment.
Just need to establish whether the regulator works or whether there is a wiring fault. Also - Make 100% certain there is no short between D and F at the dynamo, inside or out . . . Happens often enough if tags aren't carefully oriented inside, or outside connectors are poorly fitted. (Less likely  with one piece tin cover, but not sure which you have.)

[BSA500]

So far yes ammeter really mirroring the volts at the battery, keeps on rising with revs. Haven't had the chance to run other tests yet. When tested d&f together the volts acted as they should. Dynamo end cover is metal cap and this is a 12 volt wound armature with screwed on terminals not bullet

[groily]

So there shdn't be an unwanted connection between D and F then (which would bypass the regulator and give exactly the symptoms you've got).
Assuming there isn't, then you seem to me to have a regulator that won't play,  unless there is a separate prob with the F and D leads in whatever sleeving they sit between dyn and dvr2.
Suggest jury-rig of F and D from dyn to dvr if there are any 'hidden' parts of the harness to exclude that possibility, but seems probable that the regulator has gone awol from everything that you say. Could have done itself a nasty earlier on when there was confusion over the 'spare' A wires, or could just be bad luck. Easiest test is by substitution, but that's hard without one to play with I know.

[BSA500]

Well the unknown is the wiring as its a new loom so I could check for cross connection.

[BSA500]

Kay update(been away a few days). Checked green /yellow from dynamo disconnected and no cross connection. Put a probe on the d terminal of dynamo and f terminal and there was a bleep from the meter suggesting conductance. Is that not good, but it still produces plenty of volts as it should.
I found a spare DVR2 (not sure if broken or not). Put meter probes a cross d/f and got a reading of about 500,tried the found dvr and got 100 mean anything?

[groily]

There'll be connectivity between D and F, yup. Through the D brush, across the commutator to the earth brush (and thus to earth). The field coil is also (should be!)earthed one end, and the other end is at the F terminal.
We are all assuming that your dynamo is actually wired with the field coil between F terminal and earth? (Not from F to D, as per Miller systems, most 'continental' ones, or as would be necessary for a JG Regulator and perhaps some others . . .??) I think we can discount the idea that it's got 'Millerised', or you wouldn't get the output from the test you've done.
Your problem therefore seems to be simply that it isn't regulating. That might have been because D and F were touching somewhere, which would have the same effect (unregulated output) as your doing the 'bridge D to F and measure' test. But unregulated output isn't what you want off wire A to the ammeter and switch and battery.
If the voltage isn't controlled, if there isn't a short between D and F at the dyn or in the loom, and if the wiring is correctly hooked up elsewhere, then the regulator isn't doing its job.
Not sure about the 500 / 100 thing though. Just measuring from D to F leads on a brand new DVR2 in my stock, I see 210 KILO ohms give or take.

[BSA500]

The 100/500 readings come from the Continuity setting on the meter, so 500 is too much resistance(current DVR a d 100 to low)??

[chaterlea25]

Hi
One or two other things to check,
First is the battery OK, a battery that will not come up to full voltage will tell the regulator to keep charging
Check that the F wire to the dynamo does not become live when the lights are switched on (disconnect F at regulator first) this should check for weird connections in the loom...

I know that the DVR has a feature that limits current to the field coil. There are different versions to suit a 6v original dynamo converting to 12v or for dynamos that have the 12v armatures and field coils
Do you have the correct one?

A further check on the regulator would be to disconnect the battery, connect a voltmeter to the battery wires, fit a standard headlamp bulb, start the bike with the lights turned on
bring the revs up slowly while watching the voltmeter the voltage should stop rising somewhere near 14.7volts
You need a good true RMS meter as cheapo ones will tell lies on most bike electrics

A variable DC power source can also be used to check the regulators if you can source one ?

John


John

[groily]

Don't know what the reading should be across those leads, so can only tell you what I see on a brand new one (which was more than 0.2 Mega Ohms).

Good point from John about checking the  F lead, and he reinforces the earlier point about checking the regulator output (the brown A wire basically) with the battery disconnected to see it isn't open-ended as revs rise. That is exactly what you need to do as a next move. Even a cheapo digital meter will probably give you a reasonable indication, albeit spiky as I said before. You need to know what is happening here and until you do it's ****ing into the wind.

Ref the versions of the DVR2 regulator, there are just 2 - Positive and Negative earth.  The same unit, set for 12v with the white wire suppressed, is used for dynamos using original windings running at 12v, as for the after-market finer-wound  '12v' armatures and fields.  For 6v, the white and brown wires are spliced together, as it says on the sticker.

[BSA500]

OK I shall work my waythrough these tests and report back. Many thanks for all these suggestions

[Swarfcut]

 Dynamo internal wiring is detailed in previous posts in the electrical section of the Forum, including a well crafted piece by Andrew at Priory Magnetos. Also Brightspark website is well worth a look. Another outfit, The Magneto Guys, don't do dynamos but have clear info about testing and dynamo pitfalls. I searched Dynamo Wiring and Dr Google once more came up with the goods.

 Swarfy.