Ammeter showing no charge - 'Flash' dynamo?

[RoadRunner]

Thanks to all for the info so far....after a basic and more logical approach I've now have the following data with the ammeter reading below minus 8 amps as per pic:

Voltage Regulator Test

Using the 200 Ohms setting on the digital M/Meter touching M/M probes on yellow and green wires with all other V/Regulator wires completely disconnected.

M/M probes touching each other: 0.2
Original Voltage Regulator: 0.08
New ?crappy? Voltage Regulator: 1.2

Using the 2K Ohms setting on the digital M/M touching M/M probes on yellow and green wires with all other V/Regulator wires completely disconnected.

M/M probes touching each other: 0.000
Original Voltage Regulator: 0.008
New ?crappy? Voltage Regulator: 0.001

Dynamo Test
Green wire connected to Field on both Dynamo and V/Regulator
Yellow wire connected to ?D? on both Dynamo and V/Regulator

With engine running: joined both Yellow and green together (at the v/regulator end of the wires) and connected to ?ve M/M probe and +ve M/M probe connected to Earth: fluctuating voltage reading between 8.5- 15/17volts.

Using the 12v bulb test; yellow & green to one bulb terminal, other to earth: bulb got brighter upon engine been revved.   

Voltage across Battery Terminals:
Without engine running: 6.28 volts
With engine running: up to 6.50 volts upon medium revving

Ammeter Terminal Check:
Without engine running: 6.28v on +ve post and 6.29v on ?ve post

Questions:
1) Can I take it from the above info that the Dynamo is charging and that the voltage regulator is working and the ammeter at faulty?

2) Is the ammeter adjustable/repairable?

3) Is there any problem/issues with replacing the current -8amp ammeter with an original 12 amp version? If so am I likely to blow this one??

4) For an A7 Plunger what should the ammeter ?ve & +ve value be; 8 or 12 amps?

Thanks for bearing with me on this one not being an electrical wizard!
Cheers
RR

[bsa-bill]

A 12 amp ammeter will give a smaller deflection than an 8 amp one

I'm wondering if we are getting confused with your Ammeter  - and + connections

Just been out to check the wiring on an old headlamp as there's a Lucas ammeter in it
Looking down on the ammeter from the bike seat as it were, the wire that goes to position 3 on the switch should come from the negative /discharge side of the ammeter.
This is the headlamp that came on my project, can't recall if it worked right but perhaps someone can confirm that's the way it should be

[RoadRunner]

Thanks Bill,

The 2 purple wires (one goes to position 3 on the switch) are connected the -ve post (LHS as seen from astride the bike) and one brown wire connected to the +ve post (RHS).

I'm wondering if we are getting confused with your Ammeter  - and + connections

Whilst M/M testing the other day with the old v/reg in place I blew both fuses and thats when the ammeter showed a -ve value? Hence I've gone back to the new v/reg but think I've destroyed the ammeter?

Cheers
RR

[trevinoz]

RR,
          You say that you tested the reg continuity on the green and yellow wires.
The wires need to be disconnected before you test. Test between the reg terminals only.
From your testing, the generator is OK.
Your voltage test across the battery terminals indicates that you have a charge going into the battery but the voltage is a little low.
Have you tried adjusting the voltage at the regulator?
If you don't know, the regulator portion is on the left, with the terminals at the bottom.
Try screwing the adjuster screw at the rear of the chassis in, but be gentle as a small movement of the adjuster gives a fair increase in voltage.
Going back to the continuity, you should get an extremely low reading and if you press in the regulator armature [left side] the reading should increase to over 30 ohms.

  Trev.

[RoadRunner]

Hi Trev,
Again, many thanks for your help and patience  ;

The v/regulator continuity test was conducted with it off the bike hence all wires disconnected.
I did as you suggested and depressed the LHS armature which gave a reading of 0.052 (assuming I pressed the correct part as identified in the photo below).

And before I start fiddling with the voltage; presumably its the right one as identified again per the pic?
Again, I assume clockwise increases voltage; you say gently! How much of a 'screw turn' would you recommend (1/8th 1/4; 1/2 a turn)?

What should the voltage be across the battery terminals with the engine running?

As for the ammeter; I gently turned the adjusting screw on the reverse and managed to zero the needle but still wonder if its duff?

Cheers
RoadRunner

[trevinoz]

RR,
         The reading of 0.052 depends on the scale on your meter which you used.
Hopefully it translstes to 52 ohms.
The adjusting screw you indicate is correct. As to degree of movement of the screw, it's a case of suck it and see.
Try a minimal movement and check. I would be looking for a voltage of around 7.2.
As to the ammeter, it should deflect when you turn on your lights, if it doesn't you have a bad one or wrong connections.
 Trev.

[RoadRunner]

Hi Trev,
Thanks for the info - the reading of 54 Ohms was with the M/M set at 200 Ohms - the lowest setting on my M/M; the next setting being 2K Ohms? So hopefully thats okay?

The ammeter doesn't flicker one iota so I'm going to swop it for an old original one I have knocking around to see if I get an joy from that before plodding out yet more money of duff OEM rubbish.
Will post results of voltage reading after V/R screw turning and ammeter replacement later this week. Fingers crossed!
Cheers
RR

[trevinoz]

You'll get there, RR.
                                54 ohms is OK and it seems that the points are clean with the low reading that you got.
Good luck from here on!
  Trev.

[RoadRunner]

Update:
Whilst I had the 'new' OEM v/reg off the bike I drilled out the split bullet holes to the correct diameter to accept the original split bullets - to ensure they don't vibrate out; also managed to re-zero the ammeter.
Re-connected the battery today and the ammeter worked straight away? So no idea what I've done but its working. Maybe a really poor connection?? However, the voltage across the battery terminal is still around 6.30v despite turning the adjusting screw several turns. Now found a neighbouring sparky who's offered to test and set it up. Other than that she's looking good.

Cheers
RR