The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: LJ. on 20.02. 2012 16:18

Title: Confusing polarity?
Post by: LJ. on 20.02. 2012 16:18
Any idea about this please...

I switch on pilot lights or headlights and ammeter correctly, as expected, shows a discharge. However, when I apply brake, the ammeter shows a positive charge! Why is this and how the heck do I put it so it shows discharge like the pilot or headlights? The DVR2 works fine and shows a charge on the ammeter and works perfectly. I just cannot for the life of me work this one out. Got any ideas?  *dunno*

Bike is positive earth, Sealed gel battery, all wiring and earthing connections are good.
Title: Re: Confusing polarity?
Post by: bikerbob on 20.02. 2012 19:01
Hi there. I am no expert on wiring but it seems to me that you have the lights and ammeter wired up correctlly so that leaves the rear brake switch have you tried reversing leads on the switch.
Title: Re: Confusing polarity?
Post by: beezermacc on 20.02. 2012 19:05
Does this happen with the engine running or not running or both?
Title: Re: Confusing polarity?
Post by: Dynamo Regulators Mike on 20.02. 2012 20:10

The brake light circuit is normally connected directly to the battery live, not through the ammeter. The pilot & main lights are on the same side as the regulator 'A' output (other terminal of the ammeter). What you are seeing on the ammeter with the brake light on is the additional current from the dynamo though the ammeter to the bulb. The voltage is held steady by the regulator so the battery current is unchanged (as log as the dynamo is spinning fast enough).

Hope that makes sense. Probably much clearer with the aid of a diagram.

This is a normal situation resulting from the precise electronic regulation of the DVR2

Title: Re: Confusing polarity?
Post by: wilko on 20.02. 2012 21:08
This subject has come up before, don't worry about it. It's just the regulator allowing extra current into the battery to compensate for the extra draw with the brake light on. It will be more noticeable with a discharged battery.
Title: Re: Confusing polarity?
Post by: LJ. on 20.02. 2012 22:07
Aaaaaahh gotcha! I can see/understand clearly now. Thanks for the explanation... I was really pulling me hair out over this. lol Thanks again...