Hitchcocks Forum

Bullet Sixty 5 2004
Hi, having trouble with my ammeter. It has gradually been getting worse for the last 3 or 4 months, not working until I have ridden it for a few miles, but now it has stopped altogether, charging etc all ok. ………………………..
Is a 6v ammeter the same as a 12v ammeter? From what I remember of electrickery lower volts bigger conductor less insulation, sumut to do with Ohms law or his mates. So will a 6v ammeter fit on a 12v system?
And how does the ammeter come out of the casquette? Is it just prised out with screwdriver?.................Regards Fred

They are advertised by Hitchcocks as follows:

AMMETER (LUCAS) 12amp scale for 12volt systems

AMMETER (LUCAS) 8amp scale for 6volt systems

Presumably this means that they ARE different. It's what I thought but I'm no authority on that.

Taking them out: They press out, no screws or anything, except obviously the electrical connectors, but are tight.

Putting the new one in is also tight but you can use talcum powder to lubricate between metal and rubber. This works very well I've done it a few times. And smells lovely...
Make sure it is straight not at an angle so it looks ok when finished.

Disconnecting the battery first is a good idea as you're bound to touch one of the contacts...
Good luck, Chris

Hello FREDDY W,---- Talc. Powder ?? .......... you'll be making a whole bunch of new "friends", that's for sure !!----------- and what's wrong with that ?? NOWT !!......Seriously now, you could well find that some "contact corrosion" has crept between one or both of the connections of the Ammeter, OR there may well be an internal problem with the moving coil maybe ?? YES, the Ammeter is just a press fit within a thin rubber shroud and then into the casquette itself...Over the years this tends to dry and form "Stiction" making removal awkward.... First, dis-connect the EARTH side at the battery....this safeguards against the inevitable short circuit....next, peer into the gloom that is the casquette without the headlamp fitted and dis-connect the two sets of leads attached to the ammeter---remembering to keep each set separate from the other...Now, gently tease one part of the Ammeter bezel ring upwards slightly--maybe an electrical screwdriver will help ?? (enough that you can squirt some WD40 etc. in there.)... By a combination of lube oil, wriggling and pushing (Hey !!This is beginning to sound rather interesting ???)--- the meter will eventually prise free....Replacement is just the reverse and, as CHRIS said }---- apply some of that powder to help insertion (oops !! I'm at it again)... DON'T connect the Ammeter directly across the battery terminals---it'll just melt !! Put some sort of electrical load ( eg a headlamp bulb is ideal) IN SERIES with it..........Technically it is possible to "re-engineer" them, but why bother ?? They're cheap enough after all and it will only add a degree of complexity later on if/when problems arise.

Hi Both…. Thanks for both your comments. As for difference between 6 & 12 Volt ammeters I feel they are more or less the same with different scales on the face so that the 12V one will show less deflection. Right or wrong?.....................I might pick one up at Cheltenham bike jumble tomorrow. ……………..As for fitting it I can use some of the Talc that I use for getting me tights on for winter riding, but Alan, WD40 no no no always use Ponds baby oil, ooo ah memories of Amsterdam, almost as good as Castrol R on the Island, But I never seem to meet the right sort of friends. ………………………………Best regards my friends Fred

Hello there, FREDDY W --------- Oohhh, you saucy sailor you !! PONDS baby oil ??Nothing but the best for our hero it seems ?? Matey, if you can't find a "Friend" in Amsterdam then you ARE in serious trouble --LoL !! Have a look at this, but don't get too involved....... http://www.allaboutcircuits.com/vol_1/chpt_8/4.html ------- A 12v rated meter can be used in a 6v circuit but I wouldn't risk it the other way around myself (talking about your "friends, again !!).. I have a couple of spare Enfield Ammeters which you are welcome to have one FOC apart from P&P that is.....Will post photos soon.

---------here you are }------------------------------------------------------------------------------------------------------------------- ------------------

Alan, Website was very interesting and lucid but my goodness, do I really want to know about shunt resisters et al. No no no. I left all that behind me when I left work years ago.
Cheltenham bike jumble was rubbish; everybody had gone to Kempton apparently. Only half a dozen stalls there and it were damn cold on me Daytona. I took my ammeter out, same one as your black face one & found the pointer was clicky____I would dearly love to take you up on your magnanimous offer. If you could mail me at [email protected] we could sort out some details. _____________Many thanks Fred

Hi FREDDY--------------- E-mail sent.

Just a few words about amperemeters: .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

First a little basic theory, which I am shure most of you are familiar with already. But just to be on the safe side: V * A = W (when it comes to DC. AC is somewhat more complicated). .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

There is no such thing as a 6V or 12 V ammeter. The ammeter doesn’t care about the voltage. It is connected in series with the charging and battery circuit. The deflection is only dependent on the current flowing through it, not the battery voltage. As all the current flow through the ammeter, it is important that the internal resistance is small, and therefore the voltage drop across the ammeter is small. .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

The important thing is to choose an ammeter that can handle the largest currents that may regularly occur in this circuit. To use my own Model G with magdyno as an example: In this 6 V system with 45 W dynamo, 30 W front bulb, 3 W pilot bulb and 5 W rear bulb the maximum discharge is approx. -6,5 A with engine stopped and all lights swithced on. If the battery is flat, the maximum charging current is approx. +7,5 A if you don’t turn on any lights. Hence, the ammeter is a -8 – 0 – +8 A type. .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

The brake light and the horn run directly off the battery, separate from the ammeter circuit, so they don’t contribute to the current through it. This is so for two main reasons: 1. Their current draw is so large that they would “fry” the ammeter if used together with other cusers, and 2. They are on for very short periods only and don’t really matter when it comes to the battery’s charging conditions. .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

If you take the above example, converting it to 12 V but keeping the bulb wattages unchanged, the maximum dishcarge and charging currents will be only half, so a -4 – 0 – +4 A ammeter would be sufficient, if it was available. .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

This will be different on a bike with alternator etc., but the main point is still valid: The ammeter only cares about the maximum current, not the voltage. .-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-

Regards, Anders F. R.

I forgot to add: If it is a defective ammeter that causes loss of charging, you can just take the ammeter out of the circuit by connecting the two leads together on one of the connectors. Then the current will flow past the ammeter. You will of course not see how many amperes and which way they go, but as said: If the reason for no charging is a defective ammeter, this will bypass that problem and allow charging until the ammeter is repaired or replaced.

Regards, Anders F. R.