My alternator wire melted.
The ignition was still keyed on, the motor just died and the first instinct was to disconnect the battery. I changed my instrument cluster to digital and ran my own wire straight to the battery for my volt meter. That's what an ammeter is, right? Or did I wire my stuff wrong :/
oh.
Factory instrumentation:
* Uses a 5 volt regulator for the fuel level, coolant temperature and oil pressure lamp or gage .
* There is no voltmeter. A voltmeter will show Potential energy level between two points, one usually being ground. Power can not be sent through a voltmeter. Wiring a voltmeter in-line will destroy it.
* Ammeter measures current flow through a wire. Most ammeters have an internal shunt that actually carries the current. (Some later cars did have external shunts, but the point here is with a typical ammeter wired in-line. Power goes in one terminal and out the other.)
Its probably worth going over this:
Volts are potential energy. Like water in a big holding tank on a roof, even when the electricty is not flowing, it has potential to flow. In fact if we punched a big hole in the side, so much would come out it would knock a person down who tried to stop it from reaching the ground. Same idea with a battery. But what knocks him down? The water being 14 feet above ground? No. Its the hundreds of gallons rushing out of that hole 14' above ground.
Amps are a measurement of flow. If a tap at the bottom of that water tank is opened, the flow into a hose can be described in gallons per minute.
The ammeter shows how much flow is making its way from the battery to the main junction, or how much current is flowing to the battery to charge it.
In the typical automotive setup with an ammeter, the battery is connected to the rest of the system through the charging wire. Everything downstream of the battery was protected by a fusible link in that wire. If you are going to use a different wiring strategy, it still will need protection on each and every wire downstream from the battery. If you compare the 1985 wiring with the 1986 SJ Jeeps wiring you can see how that was done in a single wire (ammeter) vs an engine side distribution (voltmeter). diagrams here:
1985 AMC Jeep SJ Charging and Headlight Wiring Diagrams
