Quote:
Originally Posted by Large Arbor
I am not sure what the ammeter actually did. I mean mine did not work and I have heard of other ERA members not having working ammeters Was it just for show? What current did it measure? Seems to me, voltage is a better indicator of what is going on with the charging system which is why I am doing the switch.
Phil
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There is some misunderstanding about the ammeter in these cars. Of course, if it didn't work (meaning the needle was always just pointing straight at zero), then it's not much help anyway!
The ammeter sits between your battery, which is on one side of it, and the alternator and the electric load of the car, which is on the other side of it. When the battery is fully charged, and everything is running normally, very little current passes through the ammeter regardless of what sort of electric loads you have turned on (fans, lights, pumps, etc.). That is because both the load and the alternator are on the same side of the ammeter. As the load goes up (because you turn on your headlights, for example), there will be a momentary rush of current from the battery through the ammeter to help serve that load, but the alternator will then pick up the task and handle it -- so the ammeter needle will once again be close to zero. Likewise, right after starting your car, the battery will need some charging, so more current will be running from the alternator/load side of the ammeter to the battery -- but not for long. On a healthy battery this will only be for a short while and then the current will go back down to a dribble.
Just because you have a 100 amp alternator does not mean 100 amps is always (or ever) going through your ammeter. Plus, most ammeters do not pass all the current through the gauge itself anyway. Only a portion of it actually passes through in order to be measured. Of course, sometimes ammeters fail -- and this is their weak point. If your ammeter somehow shorts itself to ground, then the full power of the alternator will ramp up to attempt to serve what looks like a big hefty load, but what is really just a short circuit. The larger gauge wire can carry quite a bit, and will make quite a mess, along with a fire. The ERA master circuit breaker will not help with an ammeter that is shorted to ground if the alternator is still turning and producing current; it will help to isolate the battery though. A voltmeter doesn't have this problem, as very little current is going to it and, if it shorts, it will just blow a fuse like a bad bulb can -- no big deal at all. I like my ammeter, and it's more sensitive to quick changes in load than a volt gauge. So, in that regard, it's more fun to observe and will tell you more if you are really familiar with it, your car's electric load needs, and the peculiarities of the gauge itself. But if you have a systemic problem with your charging system and battery, a volt meter will tip you off just as well. And volt meters are as safe, or safer; there is no argument there.