I expect there is another root cause to the short circuit problem than the ammeter itself; look for a bad wire or other power consuming device that has an accidental ground connection. I also use and recommend these three tools to help your search:
1) The Pierce Arrow Wiring and Tuneup Guide [on our website: Member Pages -> Company store -> Book Gallery ->(last row of books, on the right side)]. I have one of these books for sorting out wire problems on my ’29, and it is very useful.
2) A Voltage/continuity meter; to measure resistance to ground of individual wires and devices, you don’t need an expensive one. If you find something touching ground that should not be, then it becomes very high on the list of suspects.
3) Test Battery. I use the Rayovac #918, a 6 volt lantern battery with screw terminals to connect your test wires. This battery has enough juice to make many accurate tests – but not so much power it is likely to fry something else. The battery in the car has too many amps for testing, and is not good at testing individual wires or devices.
Happy Hunting, Herb