Circuit and Terminal Designations

Several wiring circuit in the vehicle's electrical system are identified with a number or letter designation. These circuits are identified the same in all wiring diagram and are most commonly shown near the top of each page in the fuse/relay panel portion of the wiring diagram. the circuit designations may also be used to identify switch connector terminals (switch circuits). Following are the most common numbered/lettered circuit:

Terminal (circuit) 1-
Ignition distributor low voltage (typically used as an Engine Speed (RPM) signal for the tachometer)

Terminal (circuit) 15-
Switch Battery Positive Voltage (B+) from ignition/starter switch

Terminal (circuit) 30-
Battery Positive voltage (B+), hot at all times

Terminal (circuit) 31-
Ground (GND)

Terminal (circuit) 50-
Starter control; switched B+ from ignition/starter switch

Terminal (circuit) 56-
Switched headlight B+ from light switch

Terminal (circuit) 58-
Switched parking light, taillight. illumination B+ from light switch

Terminal (circuit) S (SU)-
Key in ignition circuit; switched B+ from ignition/starter switch

Terminal (circuit) X-
Load reduction circuit; switched B+ from load reduction relay