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#895722 11/18/22 10:26 am
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TriVin Offline OP
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Recently my Bonnie has started showing funny ammeter readings compared to normal.
Whilst cruising at 60 it shows a discharge of -4 amps but my voltmeter shows 13V constantly. When slowing down it returns to 0 or even goes +.
Put the lights on and as you would expect it shows -6. The more you rev it the worse it gets but the voltmeter stays at 13V
Same result when I swapped the ammeter for one of my Tiger 100, which always performs normally.
After the ride the battery reads 13V across the poles so charging is OK but something dodgy is going on. It has a Boyer EI.
I'm thinking that as the vibration increases something is shaking loose but not sufficiently enough to effect charging. Have not found it yet but could something else be occurring?
Any ideas welcomed.

Dave


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Does voltage rise from under 13V to about 14V when you rev up from idle?

Does it do that rise with lights on and lights off?


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Have you recently upgraded the rectifier/ regulator ?

sounds like the ...rectified alternator output... is hooked onto the wrong side
of the ammeter .
( many people mistakenly run the alternators rectified output directly to the battery , which is okay electrically , if fused )
but this will bypass the ammeter ... for bikes where an ammeter is used )
... wired this way ... the alternator output and the battery output will ...both show ammeter
Deflected to the minus Flow side .( and increased minus deflection with increased RPM )
the increase minus deflection is the alternators output flowing through the ammeter
... to bike loads ...but backwards for how ammeter should be wired .

ammeter has a plus and minus side , these are not for voltage
... they are for ....a plus current flow into the battery
.... or minus flow... from the battery

The ammeter plus ... needs to have one connection directly to the battery ( and maybe a fuse )
... and horn maybe on this side .

the rectified alternator output ( that not the earthed side ) ... needs to connect to the ammeter minus (flow) side .
( this minus side the same side as all of the bikes loads that are to be monitored through the ammeter )

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TriVin Offline OP
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TT

Yes it does rise to 14V as you would hope and expect. I have to check the wiring now as per Quinten suggests.

Dave


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TriVin Offline OP
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Hi

Well I checked the wiring but it seems to be as you described it should be.
There is a page on the GABMA website which pictorially illustrates how the typical Lucas wiring of an ammeter should be which ties in with your comments exactly.
The only other thing I have noticed is that when you switch the ignition on the ammeter does not move. On my other 2 bikes which also have Boyer ignition, when you switch on, the ammeter goes -2 as you get an immediate draw from the Boyer. Might mean something to someone more electrically minded than me!

Dave

Last edited by TriVin; 11/19/22 2:03 pm.

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I seem to recall that the Boyer Mk iii and iv on twins doesn't switch on until the crank is rotated.

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The Boyer turns on and then goes into stand-bye , in 2 or 3 seconds , if not kicked over .
Depending on the sensitivity of the ammeter , it will show a negative tick , when switched on
and if meter were sensitive enough ... meter returns almost to zero . ( if not kicked over )
( The Meters sensitivity or lack thereof may not indicate precisely what's going on )

I think all Boyer analog ignitions "throw a Spark" when first switched on
And another " one" when Switched Off . ( this used to be one of the tests )
You could run with plugs out and grounded to engine .

How many connections are on the non-earth side of the battery
the Boyer load may not be running through the ammeter ?

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I get funny amp meter readings too. My needle bounces between + and - at the speed of light. I've had a bunch of Triumphs and they all did the same. So this gauge is supposed to really work?


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TriVin Offline OP
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http://gabma.us/wp-content/uploads/2015/09/ammeters.pdf

This how I have the ammeter connected. Seems simple enough but somethings not right.

Dave


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Originally Posted by TriVin
http://gabma.us/wp-content/uploads/2015/09/ammeters.pdf

This how I have the ammeter connected. Seems simple enough but somethings not right.

the picture is incompletely labeled ( at the ammeter )
and implies ( to me ) that the ammeter is connected backwards

With all respect to the author of that article , who seldom makes mistakes .
the gamba pic is electrically OK , will function ... but functionally backwards .
the Lucas zero-center ammeter we are familiar with
has a ( plus amps ) side ( deflects clockwise from zero ) ... and a ( minus amps) side ... ( deflects counterclockwise for zero )
... the battery gets connected ... always to the plus amps side ( not labeled in the pic ) (but which looks to show battery connected to minus amps side )

1. for positive ground ... the plus amps terminal >>> goes to negitive voltage terminal . ( deflects on the positive side )
2. and the loads and rectified charging stuff ... all connect to minus side of ammeter ( side that deflects negative amps )

Using the gamba pic ... switch the input leads , side for sidė , at the ammeter and it will read correctly

the ammeter acts like a balance beam , or flag in the circuit , measuring the voltage levels ... from two different power sources .
when voltage on the charging side becomes higher than battery voltage ... the flag waves plus
... and the battery is driven chemically , by the voltage differential , back into a state of re-charging
( the battery becomes just another load on the charge circuit )
... amp meter deflects towards the battery , when battery is the lower of the 2 voltages ...
Number of amps-in , indicates the amps of charge specifically into the battery .

1. A discharged battery will have a large amp flow ( if the charge circuit is able to deliver it )
2. And charged battery it will show only a very small plus amp flow ( even if the charge circuit is able to deliver more )
... because ultimately , the resistance of the battery will stabilize to maximum regulated voltage .

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TriVin Offline OP
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Hi

I did actually spot that the GABMA diagram was sort of pictorially confusing and that the + side of the ammeter should be to the battery - side.
I have my rectified output wire breaking into the brown/white between the ammeter and the ignition switch as shown as well. Would it make any difference if I take all the way to the - ammeter stud instead? I think not although it would get rid of an unnecessary connection.
With regard to RF Whatley I have noticed that he has not posted on here recently. Has he passed away or ill?

Dave


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Originally Posted by TriVin
. . . With regard to RF Whatley I have noticed that he has not posted on here recently. Has he passed away or ill?

Dave
Dave, It looks like your intuition is correct was incorrect (thankfully), at least as far as the passing away part. Look HERE.

Last edited by TR6Ray; 11/23/22 4:14 pm.

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TriVin Offline OP
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Well that's good news then. At least we still have all that data on GABMA that he put together to refer to.

Dave


Dave
Tiger 100SS 1966
T120V 1972
Vincent Comet 1952

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