Alternator & Voltage Regulator

new 07/29/2004, updated 8/10/04

Generator
The generator (GEN) (10346):

supplies current to the vehicle's electrical system.
charges the battery (10655).
With the ignition switch in the RUN position:

voltage is supplied through the I circuit to the voltage regulator (VR) (10316).
the generator warning indicator turns on (lamp prove-out).
the voltage regulator turns on, allowing current to flow through the A circuit to the generator field coil.
With the engine running:

the generator produces alternating current (ac), which is changed to direct current (dc) by the rectifier diodes.
current is supplied to the vehicle through the generator B+ terminal (stud).
The generator warning indicator turns off.
Generator output is controlled by the voltage regulator.

Voltage Regulator
The voltage regulator (VR) (10316):

adjusts the generator field current to increase or decrease generator output current.
sets the generator output voltage.
turns the generator warning indicator on when a problem is detected in the charging system or associated wiring.
The generator output voltage will vary with temperature. The output voltage is typically higher in the winter (cold) and lower in the summer (hot).

The voltage regulator will turn the generator warning indicator on for the following conditions:

ignition switch in the RUN position with the engine not running. This is the lamp prove-out (does not indicate a problem with the charging system)
open in the A circuit
inoperative generator (GEN) (10346)
generator output voltage too high
Refer to Section 14-00 for diagnostic procedures if the generator warning indicator stays on with engine running.

With the system functioning normally:

the generator output current is determined by the voltage of the A circuit (battery-sense voltage).
the A circuit voltage is compared to a set voltage internal to the voltage regulator. The voltage regulator controls the generator field current to maintain proper generator output.
the set voltage varies with temperature and is typically higher in the winter than summer, allowing for better battery charging.
The generator warning indicator comes on when a problem is detected in the:

generator.
voltage regulator.
associated wiring.

SPECIFICATIONS

GENERATOR SPECIFICATIONS
Item	Specification
Generator (10346)	F5OU-AA
Generator Rating (idle/max. rpm)	(130 Amp max)
Generator Ratio (gen. crank/rev.)	2.4:1
Regulator Type (10316)	Electronic/Integral with Generator

NOTE: The voltage regulator (VR) (10316) is the only internally serviceable component on this generator (GEN) (10346) .

PINPOINT TEST B: SYSTEM OVERCHARGES (BATTERY BOILS OVER)

B1 CHECK VOLTAGE DROP IN A CIRCUIT

Turn ignition switch to RUN.
Measure voltage between A terminal on the voltage regulator and the positive (+) battery post.

Is voltage drop less than 0.25 V?

Yes	No
GO to B2	SERVICE excess voltage drop in Circuit 35 (O/LB). CHECK Alternator Fuse (30A) and connectors in Circuit 35 (O/LB) and SERVICE as required.

B2 CHECK VOLTAGE DROP IN I CIRCUIT

Measure voltage at connector C154 I terminal, Circuit 904 (LG/R).
NOTE: Voltage regulator must be connected to wiring harness for this test.

Is voltage greater than 1 V?

Yes	No
GO to B3	SERVICE high resistance in Circuit 904 (LG/R).

B3 CHECK FOR POOR GROUNDS

Check for poor ground connections between voltage regulator and generator, generator and engine, or engine and battery.

Are all ground connections clean and tight?

Yes	No
REPLACE generator.	CLEAN or SERVICE grounds as required.

My thanks to the Mysterious Middle Earth Contributor

U.L.

Hmmm, mysterious eh??

Should change the title to "Alternator and Regulator-Overcharging" as that is the issue and diagnostic procedure.

Or I could just give you all of it.

Paul