ammeter/bypass problems

Here is the Mad electrical article, should you decide to completely bypass the ammeter. Lots of people have done it, especially when the ammeter fails, which could be your problem. You'll just need to check it for continuity to ground with a meter at each terminal. If either terminal has continuity to ground, the ammeter has failed. You'll want to make sure to do that with both wires disconnected from the ammeter, as to isolate it.