Electrical System
366
On-Vehicle Charging System Checks
Troubleshooting No-Charge Condition:
Following is a step-by-step troubleshooting procedure. An experienced technician may use the schematic
and skip some of the procedure steps. See Figure 9-12 for charging system schematic.
1. With engine not running, connect voltmeter across battery; voltmeter should indicate approxi-
mately 24 volts.
2. Leave voltmeter connected across battery; start engine and run at fast idle.
a. If voltmeter indicates 28 volts, battery is being charged. The problem is probably in the No-
Charge indicator light circuit. Check the fuse rst, then troubleshoot circuit.
b. If voltmeter remains at 24 volts, the No-Charge indicator light is correct and the battery is not
being charged. Proceed to next step.
3. Connect voltmeter to alternator POS terminal.
a. If voltmeter reads 28 volts, troubleshoot for open circuit between alternator and battery
(check 325 amp fuse rst).
b. If voltmeter reads low voltage, proceed to next step.
4. With the engine running, connect voltmeter positive lead to alternator F2 (ground) terminal and
negative lead to ground.
a. Voltmeter should read 0 volts.
b. If voltmeter reads a voltage, even if very small, a poor ground connection exists and must be
corrected before the system will operate properly.
5. Connect voltmeter to alternator F1 (eld) terminal.
a. If voltmeter reads 28 volts, alternator is defective.
b. If voltage is 0 or less than 28 volts, proceed to the next step.
6. Switch the battery disconnect switch to the Off position. Unplug the harness connector from
the voltage regulator. Plug a break-out tool (Gillig part number 50-57843-000) into the voltage
regulator, and plug the harness connector into the break-out tool. This will allow you to test volt-
age regulator connections while the harness is connected and with the engine running. Refer to
Figure 9-12. Connect voltmeter (+) lead to the NEG terminal of the break-out tool and voltmeter
(–) lead to ground.
a. Voltmeter should read 0 volts.
b. If voltmeter reads a voltage, even if very small, a poor ground connection exists and must be
corrected before the system will operate properly.
7. Connect voltmeter to regulator FLD terminal.
a. If voltmeter reads 28 volts and Step 5 indicates less than 28 volts, there is a wiring problem
in the eld circuit between the alternator and regulator.
b. If voltmeter reads 0 or less than 28 volts, proceed to next step.
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