Generator

The generator is a serviceable component. If there is a diagnosed failure of the generator it must be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it induces an alternating current (AC) into the stator windings. The AC voltage is then sent through a series of diodes for rectification. The rectified voltage has been converted into a direct current (DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge. The voltage regulator integral to the generator controls the output of the generator. It is not serviceable. The voltage regulator controls the amount of current provided to the rotor. If the generator has field control circuit failure, the generator defaults to an output voltage of 13.8 volts.

Auxiliary Battery (TP2)

The auxiliary battery provision (TP2) can be used to supply electrical power to additional equipment that the customer may choose to add, such as a slide-in camper or trailer, without discharging the vehicles primary battery. The auxiliary battery relay closes when the engine is running, in order to allow the generator to charge the auxiliary battery. The relay opens when the engine is off, so that the accessories will not discharge the vehicles primary battery, which is used for engine starting. If the vehicle is equipped with an auxiliary battery, the relay will be located on the driver's side of the vehicle, next to the underhood electrical center. Generally, a fuse should not be used in the STUD 1 Fuse 70 position of the underhood fuse block, if the vehicle is equipped with an auxiliary battery. A plastic plug may be installed in this position instead of a fuse. If a fuse is installed in this position, the accessories will discharge the primary battery in addition to the auxiliary battery.

Schematic Reference:

Connector End View Reference:

Component Connector End Views

Description and Operation

Electrical Information Reference

1. Ignition ON. Verify that no generator or battery current sensor DTCs are set that would cause a charging system concern.

⇒	If DTCs are set, go to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Ignition OFF, measure the voltage across the battery terminals. The voltage should read 12.0 volts or greater at room temperature.

⇒	If not within the specified value, charge and test the battery before testing the charging system. Refer to Battery Inspection/Test .

3. Go to Circuit/System Testing.

Generator

1. Verify that the battery cable terminals are clean and tight.
2. Connect a carbon pile tester to the battery.
3. Start the engine and increase the engine speed to 2,500 RPM. Place the vehicle in tow/haul mode. Observe the voltage reading on the tester. The voltage should read between 12.6 - 15.0 volts.

⇒	If not within specified range, replace the generator.

4. Adjust the carbon pile tester to the specified load test output value, refer to Generator Usage .

⇒	If less than the specified value, replace the generator.

5. If equipped with an auxiliary generator, repeat this test, with the carbon pile tester's inductive pickup clamped around either generator harness.

Auxiliary Battery Charging/Isolation (TP2)

Perform this test if there is a concern with the charging of an auxiliary battery.

Do not perform this test if the vehicle is not equipped with an auxiliary battery (TP2).

1. Disconnect the auxiliary battery. Refer to Auxiliary Battery Replacement .
2. Verify that there is not a fuse installed in the STUD 1 socket of the underhood fuse block. There may be a plastic plug installed in this position, instead of a fuse.

⇒	If there is a fuse installed, remove the fuse.

3. Verify that the trailer harness, or other accessory, is connected to the underhood fuse block stud 1 terminal X7-1, if desired. Verify that the connection is clean and tight.
4. Ignition OFF. Verify that there is 0 volts present at the underhood fuse block stud 1 terminal X7-1.

⇒	If there is voltage present at stud 1, test the auxiliary battery relay and the run relay for a stuck closed condition. If OK, test the auxiliary battery positive cable for a short to voltage.

5. Start the engine. Verify that there is greater than 12 volts present at the underhood fuse block stud 1 terminal X7-1.

⇒	If less than the specified value, test the following components for an open/high resistance:

•	SEO B1 fuse

•	125 A MEGA fuse

•	Fusible link 2

•	Fusible link 3

•	Auxiliary battery relay

•

Run relay

6. Reconnect the auxiliary battery.

Auxiliary Battery Relay and Run Relay (TP2)

1. Ignition OFF, disconnect the relay.
2. Test for 60-180 ohms between terminals 85 and 86.

⇒	If not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 20 amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87.

⇒	If greater than specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.