Alternator - fuse or not.

[lw395]

This car ammeter has no electrical connections at all Therefore no risk of shorts to a metal panel

Moving Iron meter I presume? Or even moving magnet?
I spent ages years ago trying to sort the charging system of a BSA 650.
It turned out the ammeter responded more the engine vibration than the charging current!
To be fair, there was a lot of vibration and not much current.

 

[Graham_Wright]

The way it's being held suggests putting a bit of spin on it as it's hurled towards the skip.

Don't decry value engineering!

I recall, back in the seventies, a Smith's employee being awarded £1000 for a suggestion put forward for a speedometer assembly which saved 1p (might have been 1d!).

 

[Graham_Wright]

Open the meter, take the shunt out, wire the shunt in the alternator output cable.
Run small wires to the remnants of the meter and recalibrate it. Might need to shave the shunt's width a bit to up the volts to allow for extra length from shunt to meter
Do fuse the teensy weensy wires that are now connected directly to alternator output, they dont handle 60A too well

I had an incident (still to be investigated and sorted) when, on returning to the boat, I found the engine battery showing 8.2 volts and the alternator too hot to touch.

On checking everything and finding nothing, the alternator declined to charge. Stripped down and the windings disconnected from the diodes, I found nothing wrong. Re-installed and engine running. there was no charge. The "ignition light" did not light. There was 12 volts at the excitation terminal.

I eventually found that the high current had caused local heating at one of the meter terminals and it had gone high resistance. Seizing the excuse to do as others have suggested, I opened the meter to remove the shunt. There wasn't one. It appears the magnetic effect of the current inside was sufficient to deflect the needle.

I now need to find a replacement meter cosmetically as before but with a coil movement. How can you tell from a picture?!

I wonder what technology is employed in a car voltmeter. If that is moving coil, I could swap the dials. It only needs to measure in one direction.