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Hi - I have recently acquired a 156, 2.5 v6 Sportswagon to scratch my Alfa itch. I don't use it every day but keep it for weekend runs. I am busy fitting a set of Smith gauges in the dash. I am a bit stumped on the ammeter. I thought I could just run the 10 gauge wire coming off the battery positive through the ammeter and back again to complete the circuit but I get no readings what so ever. What I know about electrical circuits and wiring is frightening so I am hoping someone here can give a bit of guidance. The voltmeter and oil pressure gauges are perfect.
 

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There are some problems:

Your alternator can produce 120 Amps (probably) which is far too much for the 30 A gauge.

Both the positive and negative side of the alternator share the starter’s cables so some re-wiring would be required* to separate the positive side. Assuming you have a fuse box directly connected to battery positive it too would have to be re-wired.

So it’s possible but difficult. The voltmeter tells you most of what you need to know about the electrics, so how about an oil pressure or temperature gauge? Probably more useful in a hot climate (though I don’t know where you would fit the sender).

* The starter draws up to 1000 Amps so it’s current must not be put through the gauge.

Edit: Oil temp gauge! I've just seen you have pressure already.
 

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Thank you, RT for the advice. These gauges were my Dads and came out of his Guilia Super so for me, its sort of a legacy thing to show them off in an Alfa.
I doubt I could find a matching gauge to replace the ammeter as these are about 50 years old. I may make a new backing and just do the two gauges.

There may be a circuit that only draws partial amps which can be measured. The data would be useless but the gauge would work and that would be fine for me.
 

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I took a look and old Smiths gauges are available on ebay and new lookalikes from various places, but I take your point about originality. Good luck with it.
 

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In the "old days" the ammeter was wired in series with the main output of the dynamo or alternator (most of which were about 45amp) .. I don't think "moderns" use the same wiring principles ..

A volt meter would be easier ..

If these are Smith's gauges, you can still get them for classics ..
 
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