ammeter

All current to & from the battery goes thru the ammeter (exc. transient under-hood loads -starter & horn). If the ammeter isn't working, it may not be conducting current, and thus your battery won't charge or provide power (do headlamps work w/ ignition off?). This is for the factory wiring. Many people bypass the ammeter by running alternator output to BATT+ (on starter relay). Perhaps you did that.