NTBA

General Wiring Schematic

This is a complete wiring diagram. Before you begin to wire your hotrod take some time to study the components and get familiar with them. Basically, you need 2 positive power lines. One that is direct (no on/off) and a switched power line. If you look at the schematic, you will see a heavy red wire originating from the battery. This is your UN-SWITCHED power line. Part of the line includes a single 30 amp (main fuse) circuit breaker going to the vehicle accessories in the event of a short. The other part of the line goes directly to the starter & alternator and does not include a circuit breaker! The line that has the circuit breaker supplies power to: Ignition, lights, turn signals, gauges, starter soleniod, and all accessories. The main thing to remember when connecting anything functional to the power line is, that if it requires positive voltage, it also requires a good ground connection as well.

There are some variations in any circuit application, and you need to modify your schematic accordingly. For example, this schematic illustrates a "one wire" GM alternator, but you may have a three wire alternator. Or, you may not want turn signals.

The single biggest mistake people make when wiring is they do not use the proper size wire. This is extremely important! It's OK to have a wire too big, but if it's too small you are in trouble. Wire size is determined by how much load it will carry and how long the wire is. The second mistake people make is they don't color code their wires. Color coding is a real benefit when you encounter a wiring problem.

Wherever possible, use polarized connectors to simplify installing & removing things such as your instrument panel. Use zip ties to bundle your wires and hold them secure. When wiring any component, IE lights, horn, turn signals, and other accessories get in the habit of PRE-TESTING the circuit. In other words, make sure the circiut functions properly prior to bundling all your wires together.

The single biggest mistake people make in doing their own wiring is not completing the circuit with a good ground connection! Get in the habit of making good ground connections! You would be amazed how strangely your assessories will behave if they don't have a good gorund connection!

Any voltage that is less than the supply voltage is considered "B-". So in essence, your negative battery post is "B-", and your positive post is "B+", (your supply voltage). If you have a long light weight wire pulling a fair load, then the resistance of the wire would lower the supply voltage. If you measure the volts across the load, you would see that the voltage is lower than the supply voltage at the battery. (The resistance of the wire is consuming power in the form of heat). The difference between the voltage readings is your "current" loss. This difference of voltage is also negative, relative to the supply. Meaning, that there is a "ground" effect from the hot wire. This is where the term "floating ground" comes from. So in order to eliminate the "floating ground" effect, you need to have all the wiring the correct size for the load it's intended carry, and a good ground connection.

As illustrated, it is a good idea to have a central fuse block. This is the core of power to your entire vehicle. The central fuse block makes it easier to "trouble shoot" wiring and component faults.

Illustration courtesy of Doug "DOC" Litster

voltloss.jpg (26769 bytes)

This is a "WORST CASE" scenario, and accurate in what typically happens when you select the wrong wire gauge for the application(s)! The wire gauge for this circuit is TOO SMALL, thus causing a voltage drop between each component on the circuit. You will notice that the Ignition system only has 10.8 volts available, and the Electric Fuel Pump only has 11 volts, while the Electric Fan only "sees" 11.5 volts. While the voltage loss to the FAN isn't significant, it does lower the avaialble voltage to the Fuel Pump. This in turn lowers the available voltage to the Ignition.

The total resistance to any load INCLUDES the ground wire as well! If the 16 gauge wire were changed to a 12 gauge, then the voltage loss would be signifigantly reduced.

LOAD "A" volts=11.999

LOAD "B" volts=11.958

LOAD "C" volts =11.948

I do not recommend having multiple "high load" devices on the same hot wire, as illustrated. This creates a lot of electrical problems! The Electric Fan and the Electric Fuel Pump should be on a power line all to it's self.

In the circiut above, the combined total load is 17 AMPS. That is too high for a 16 GA. wire. It will eventually get HOT.

Plan your electrical circuit carefully!