i can read a shcematic well but have a question about the numbers that are printed next to the wires. are they the circut number or do they mean somehting else?

if it is the number next to the color then it is the gauge of that color of wire

Actually, it depends. On GMs, the older wiring diagrams have the wire gauge. On the newer (and much, much more complicated) GM wiring diagrams, they have two numbers, the wire gauge (in oh, so helpful metric) and the circuit number.

Had to chuckle on that, thanks for the wisecrack

Doc here,

Actually , unless the harness is wire marked (heat/Ink stamped), the only information you really need, is the pin number, Wire color and (hopefully) Gauge and termination of the wire. the other numbers won't correspond to anything you can decipher on the "Real World" harness.

Doc

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I don't know about that, Doc. On my 86 and 99 Chevy trucks, the wiring diagrams are multi-sheet black and white affairs. The 86 is the worst, since the diagram doesn't even show point-to-point wiring, just connectors branching off of a main line. (GM interestingly went back to point-to-point diagrams in the 99 service manual) Use of the circuit numbers is mandatory to properly trace the circuit. In addition, the troubleshooting tables in the FSMs call out circuit numbers for testing. Even the connector pinout diagrams use circuit numbers, not wire colors.

Note that I never said this was an improvement, although I understand the reasons. Complex wire harnesses like this are tested for continuity and isolation after fab with automated test equipment. The programming in that system sees only circuit numbers, not colors. At work we do the same thing with wire harnesses for aerospace systems.

got to love the engineers.

have they ever had to turn a wrench