Wire size/gauge selection for 12 volt circuits
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
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Thanks to Steve Odell for sending me this very useful information about how to select the proper gauge of wire. Please use this information in combination with Electricity usage by component and Ohm's law calculations. A note from Steve:
You will see in that chart that you can nearly wire your entire bike with 18 AWG. Many professional wirers always go up one size for a couple of reasons. One is to simply give yourself a safety margin. But the other reason, which I think is even more important, is that 18 AWG can be really hard to terminate. Connectors usually come in a range and 18 would be at the small end of that range so the connector, if not terminated perfectly, can be loose. As you know, a loose connector will cause so much resistance that the 18 AWG wire will act like a much smaller gauge and will heat up at the connector. Going up one size to 16 gives you more meat to grab when you terminate. I only use 18 gauge on stuff like idiot lights in the dash or 85/86 triggers on a relay and places where physical space is the biggest consideration for the wire.
Amperage Length of wire 3 ft 5 ft 7 ft 10 ft 15 ft 20 ft 25 ft 0 to 5 18 18 18 18 18 18 18 6 18 18 18 18 18 18 18 7 18 18 18 18 18 18 18 8 18 18 18 18 18 16 16 10 18 18 18 18 16 16 16 11 18 18 18 18 16 16 14 12 18 18 18 18 16 16 14 15 18 18 18 18 14 14 12 18 18 18 16 16 14 14 12 20 18 18 16 16 14 12 10 22 18 18 16 16 12 12 10 24 18 18 16 16 12 12 10 30 18 16 16 14 10 10 10 40 18 16 14 12 10 10 8 50 16 14 12 12 10 10 8 100 12 12 10 10 6 6 4 150 10 10 8 8 4 4 2 200 10 8 8 6 4 4 2