Instant loss of charging... car is now dead on road...

I had this same problem with a dodge pickup a few months ago. The ammeter is in series and mine went bad read dead center but the circuit was not complete because of the ammeter being popped. Also check your bulkhead connector for corrosion, terminal fittiment, pins backed out etc. after i bypassed my ammeter the right way and installed some fusable links inline mine charged around 14.5 all day long at the battery