I ran my hoe for a few hours yesterday and when I went to restart it the battery was weak. I checked and the alternator wasn't charging. The problem wasn't hard to find or fix because the wire had just broken off the B+ terminal. The weird thing is the indicator light was still operating normally. It came on with the key on and went out when I increased the engine speed.
Hmm...I am now thinking it isnt so accurate.
The alternator was still charging just was not supplying the batterys
Yeah the tach was still working also. Just wasn't connected to the battery any more.
If you had an ammeter you would have spotted it
Maybe, maybe not, an ammeter only shows if the battery is charging or discharging. If it's not terribly precise, and most weren't, it didn't show if it was a slow charge because the battery was full, or a slow discharge because the battery was almost dead. A voltmeter is cheap these days, and is better than an ammeter or a charging indicator light. I suspect accurate voltmeters were much more expensive than ammeters back in the day, that's the only reason they were used.
I am forgetting about the low quality that used to be used. Old cars were the same. I am used to using precise equipment.