Probe the test points in the fuse panel with a test lamp or a meter set on at least 20VDC.
I usually use the unpainted E-brake pedal bracket for my ground connection. Most of the cab grounds terminate here...
BATT = Power from the fusible link on J-Block studs bolted to the firewall that feeds the Ignition switch and the LH side of the fuse panel. If the 20A ATC
IGN fuse is blown there will be no power on this point.
IGN = Power with the ignition switch in
RUN.
ACC = Power with the ignition in
RUN & ACC.
LPS = Power from the headlamp switch rheostat to the instrument lamps through the 5A ATC
INST LPS fuse. Only on with the parking or headlights switched on.
PWR = Power from the Fusible link on the Starter.
Click to enlarge picture.
