When I'm not connected, my arrow points slightly to the left, but as you can see it's not designed for accurate measurements. There is no light for night driving, but that suits me. The connectors on the back are long and open, so be careful when installing them. If these terminals are shorted to ground (e.g. the frame or most metal parts) you can cause a fire if you don't use a fuse or switch. Finding installation instructions was an awfully long search, so here are my instructions: Use 8 or 10 gauge wire. Everything must go through the ammeter except for the starter motor (which requires 2 or 4 gauge wire and the ammeter will fry). The battery and starter are on the same side of the ammeter. Generator and everything else on the other side of the ammeter. I had to be creative as the alternator and many components were originally connected to the starter. It measures current flow to or from the battery (except for the enormous amount of current needed to start a car). If the arrow points to the left, your battery is draining. During the charging process (within a few minutes just after starting the vehicle), the arrow is on the right side. Normally the arrow should be at or near zero. When the engine is not running and the courtesy light is on, it should point slightly to the left. With the engine off and the headlights on it should be clearly to the left - maybe 20 amps. For a minute or two after starting the vehicle, the arrow may point 5-15 amps to the right (charging). As you cycle something on and off, the arrow may flicker one way or the other before the voltage regulator adjusts the alternator. Stopping at a red light or idling can easily drain the battery on some vehicles, but should be carefully recharged at higher speeds. If the ammeter isn't showing normal readings, something is wrong somewhere that can drain or burn your battery - possibly the voltage regulator, which is often built into the alternator. Most cars no longer have an ammeter due to the risk of fire. If you cut or short that 8-gauge wire that connects directly to the battery, it can deliver a lot of current, even with a fuse. Even with a fuse, you can set off a good firework of sparks before the fuse blows. Be careful and smart.
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