Medium and Heavy Trucks
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Yes, you have a battery disconnect switch. It is located in the left fender compartment. This must switch to the on position to complete the ground to frame circuit. If you think it has failed, use jumper cables to bypass the switch and connect from the battery ground to the chassis.
Please remember, this is a 24 volt system and you have a second battery on the right side. You will need to ground the battery on the right side to bypass the switch. The right battery is connected to ground and the left battery is connected to the starter (positive-RED-cable).
Check for power to the breakers and fuses. Clean any corrosion.
Check battery cables for continuity and clean connections
Check connections to the harnesses connecting to the dash.
Battery power comes from the batteries to the starter post and then back up a 6 gage wire to the breaker (locate near the fuse panel) then to the fuses and on to the dash and keyswitch. The key switch then powers a main relay (located back at the fuse panel) and that will power other accessories.
No sensor will turn off power to the dash. Only a neutral switch is in the circuit to verify transmission is in neutral to prevent cranking.