Electrical Wiring Diagrams

Wire Sizes
Wiring diagrams also indicate the wire gauge used (shown in mm2), designating the cross
sectional area of the wire. Because standards exist for the maximum permissible voltage drop
across a circuit, wire gauge is critical. If the voltage drop across the wire is too high, one or more
of the following may occur:
� The circuit may overheat
� The load may not operate properly (due to low voltage condition)
� Components may be damaged
If a wiring repair needs to be made and metric sized wire is not available use American Wire
Gauge (AWG) sized wire.
Note: If the exact size wire is not available for a repair, use the next larger size.
Connector Pin Assignments
Wiring diagrams tell the user at which pin numbers the wires terminate, simplifying diagnosis.
There are 4 main types of terminal designations:
� Push-on/multi-point connections
� Component/multi-point
� Central/relay panel
� Relay
Generally, pin assignments are labelled on the plastic hard-shell connector housing and/or the
corresponding component. On larger connectors, pin assignments are labeled at either end of a
row. For example, the Engine Control Module (ECM) plug often has 4 to 10 rows of 12 or more
terminals. Each row will be marked on each end to facilitate easier diagnosis.
Components
Components in wiring diagrams are given an alphanumeric designation for identification. The
first portion of the code separates the component into basic groups. An F for example, designates
a switch, while a Z would be used for a heating element.