Circuit and Terminal Designations

Several wiring circuits in the vehicle's electrical system are identified with a number or letter designation. These circuits are identified the same in all wiring diagrams 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 circuits:

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