The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: hdawson on 20.08. 2017 08:58

Title: ammeter dial operation
Post by: hdawson on 20.08. 2017 08:58
Hi all.
Another dumb question so please bear with me.
Both the BSA and the Matchy's ammeter dials bounce around while I am riding.
Is this normal?
With the engines not running , when I turn the lights on, they show the expected discharge.
But I would expect when I rev, that the ammeter needle would increase accordingly but it seems not to be.
What should I expect to see , at rest , and while being enthusiastic?
Cheers, Hadrian.




Title: Re: ammeter dial operation
Post by: Billybream on 20.08. 2017 09:10
I think you will find most of them bounce around during riding, most probably down to the poor quality of pattern items these days.
Title: Re: ammeter dial operation
Post by: Greybeard on 20.08. 2017 09:12
These little ammeters are hardly scientific instruments.

With headlight on, engine ticking over you should see a discharge but when you increase the engine revs you should see the ammeter move toward the nuetral position or a small positive charge.
If your battery is fully charged you should not see very much positive indication.
Title: Re: ammeter dial operation
Post by: hdawson on 20.08. 2017 09:35
Thanks for the feedback.
Spending too much time blatting on the modern Triumph whilst mulling on stuff I shouldn't.
 
Title: Re: ammeter dial operation
Post by: JulianS on 20.08. 2017 09:52
The original Lucas ammeters, rather than the "new" lucas ones had a small adjuster on the underside which allowed you to increase pressure on the needle pivots and if done carefully can reduce the wild swings seen when bike being ridden.

It wont improve accuracy though!

First photo shows the screw on the type with needle above dial face.

Second photo shows type with needle below dial face, screw is under the sealing gunge.
Title: Re: ammeter dial operation
Post by: terryg on 20.08. 2017 11:53
Try searching the forum for oil in the ammeter.  There have been several posts referring to how people used to fill with damping oil in an attempt to overcome the seemingly random indication issue.
I've not tried it myself but have been very tempted at times!
Title: Re: ammeter dial operation
Post by: morris on 20.08. 2017 12:25
Badly earthed dynamo can give the same symptoms.
Title: Re: ammeter dial operation
Post by: Greybeard on 20.08. 2017 12:26
I have one of these gizmos shining into the side of my ammeter. Not really visible in daylight but handy in the dark. Available in 6 or 12v:
https://goo.gl/9WH5K6 (https://goo.gl/9WH5K6)
Title: Re: ammeter dial operation
Post by: Black Sheep on 20.08. 2017 14:18
I used to be troubled by bouncing ammeter needles and did indeed resort to filling ammeters with thin oil. However, since I switched to electronic voltage regulators (for both dynamo and alternator equipped bikes) the ammeters are models of good behaviour. Coincidence?
Title: Re: ammeter dial operation
Post by: Greybeard on 20.08. 2017 15:57
...since I switched to electronic voltage regulators (for both dynamo and alternator equipped bikes) the ammeters are models of good behaviour. Coincidence?
I must say, I haven't noticed my ammeter, (modern replacement) needle bouncing around. I too have a DVR2 regulator, (highly recomended by the way).