Just a note on ammeter and voltmeter...
ammeter tells you at what status your alternator is working
voltmeter tells you what voltage/charge your battery/system is at
However, voltmeter doesn't tell you much if your bettery is on the last leg. As voltmeter is connected after the ignition switch, when a car is started, the alternator starts to work and will display a healthy 14 - 14.5v. But then the alternator may be charging at 60A even after 1 hours of driving. If so, the battery is not holding charge and will be at its last legs. Conversely, if the ammeter shows that flows reduce from say 50A to 20A after sometime driving, and the voltmeter is holding charge at 14 - 14.5v, then the system is working fine.
So, by combining an ammeter and voltmeter, I can monitor both the alternator and battery status at the same time.
1) ammeter showing high amp, voltmeter showing high voltage......okay
2) ammeter showing low amp, voltmeter showing high voltage...okay
3) ammeter showing low amp, voltage on voltmeter decreasing.......alternator problem
4) ammeter showing high amp, voltage on voltmeter decreasing.......battery problem
5) ammeter showing high amp on prolonged period, voltage on voltmeter decreasing.......battery problem
Reason for this is, often while greelaning/off roading, the alternator may get 'contaminated' by debris or mud and not functioning as it should. At this time, you are draining the battery while continuing the journey and will eventually come to a hault where the battery has insufficient charge. If known earlier, a quick service/wash to the alternator can prevent unnecessary breakdown.
Hope it make sense..!!