[TR] Ammeter shunt

[G.D. Huggins]

Anthony,

I've got the same kit and installed it this past summer on my TR4A.
I followed the instructions for the "shunt option" (described on page 9 of the
booklet) to a "T", and the stock ammeter just doesn't move.
At one point I went so far to confirm that the reconditioned ammeter was
actually working, which it was.

>From all appearances, I surmise that the shunt option from the Master's
instructions just doesn't leave enough current to flow through the ammeter.
In other words, the shunt actually carries all the charge, instead of roughly
half, leaving hardly anything for the ammeter.

In the end, I installed a voltmeter.

If you do a shunt, use Randall's approach, as it might actually work.


On Nov 8, 2011, at 10:45 PM, Randall wrote:

> There are different approaches; mine is quite a bit different than Dan's.
>
> What I did (the first time) was to undo the ammeter mounting and let it
> (carefully) hang out of the dash while I experimented with adding strands
of
> steel wire across the ammeter terminals.  I first noted the needle
> deflection with the headlights on; and then added strands of steel "handy"
> wire until the deflection was about half of it's original amount.  As I
> recall, the wire was about 18 or 20 AWG, just ordinary steel "handy" wire
> (aka baling wire) and I wound up with 3 or 4 strands of it, just long
enough
> to reach across the ammeter terminals.  Once I was happy with the division
> ratio, I reinstalled the ammeter in the dash, with the wires still in
place.
> That setup worked fine for many years, with my 60 amp Ford alternator.
>
> More recently I got fancy, and measured the resistance of several TR3
> ammeters.  From that measurement, I calculated the length of insulated
> copper that would produce the same resistance, and added that across the
> terminals.  Here's a photo taken as I was disassembling the car after it
got
> wrecked:
> http://fwd4.me/0gSZ
>
> According to my notes, I measured the resistance at 1.6 milliohms (or 0.016
> ohms, obviously not with an ordinary ohmmeter), and used 3.5 inches of 16
> AWG copper wire.
>
> But of course before applying either approach, you'll have to straighten
out
> your wiring so the ammeter reads current to/from the battery.  It may have
> changed later, but the instructions I got from Dan show this as the "60 amp
> ammeter option" in figure 9.
>
> -- Randall
>
>
> triumphs at autox.team.net
>
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe/Manage:
http://autox.team.net/mailman/options/triumphs/guy@genfiniti.com