Batt light but system still charges
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From: Savannah Georgia
After a quick review of the attached schematic, the LR3 charging system does not depend on the "battery bulb" to be present like in trucks such as the D1 and D2. You will note in the attached schematic that the generator (alternator) has four connections, the + power out to charge the battery, two leads that go off to the ECU for monitoring, and a fused sense lead from a five amp fuse , Fuse 20E, in battery junction box. If the alternator monitoring lead, white & green, were disturbed or dirty connection, the ECU would consider there to be problems and cause the lamp and messages to happen. But amps to battery may remain good.
With alternators, they have multiple windings set up as three phases to get more amps effciently. Each phase is rectified by diodes and becomes the power. One diode can go out, you'll have correct voltage, but you drop 33% of the amp output capacity. So a complete test of an alternator involves monitoring it under load, not just at idle.
From the LR3 shop manual:
4.4L)
With alternators, they have multiple windings set up as three phases to get more amps effciently. Each phase is rectified by diodes and becomes the power. One diode can go out, you'll have correct voltage, but you drop 33% of the amp output capacity. So a complete test of an alternator involves monitoring it under load, not just at idle.
From the LR3 shop manual:
The Generator has a multifunction voltage regulator for use in a 14V charging system with 6÷12 zener diode bridge
rectifiers.
The ECM monitors the load on the electrical system via PWM signal and adjusts the generator output to match the
required load. The ECM also monitors the battery temperature to determine the generator regulator set point. This
characteristic is necessary to protect the battery; at low temperatures battery charge acceptance is very poor so the
voltage needs to be high to maximise any rechargeability, but at high temperatures the charge voltage must be restricted
to prevent excessive gassing of the battery with consequent water loss.
The Generator has a smart charge capability that will reduce the electrical load on the Generator reducing torque
requirements, this is implemented to utilise the engine torque for other purposes. This is achieved by monitoring three
signals to the ECM:
rectifiers.
The ECM monitors the load on the electrical system via PWM signal and adjusts the generator output to match the
required load. The ECM also monitors the battery temperature to determine the generator regulator set point. This
characteristic is necessary to protect the battery; at low temperatures battery charge acceptance is very poor so the
voltage needs to be high to maximise any rechargeability, but at high temperatures the charge voltage must be restricted
to prevent excessive gassing of the battery with consequent water loss.
The Generator has a smart charge capability that will reduce the electrical load on the Generator reducing torque
requirements, this is implemented to utilise the engine torque for other purposes. This is achieved by monitoring three
signals to the ECM:
��
Generator sense (A sense), measures the battery voltage at the Central Junction Box(CJB).
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Generator communication (Alt Com) communicates desired Generator voltage set point from ECM to Generator.
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Generator monitor (Alt Mon) communicates the extent of Generator current draw to ECM. This signal also
transmits faults to the ECM which will then sends a message to the instrument pack on the CAN bus to illuminate
the charge warning lamp. For additional information, refer to
the charge warning lamp. For additional information, refer to
Generator (414-02B Generator and Regulator -
4.4L)
Last edited by Savannah Buzz; Feb 15, 2013 at 06:11 AM.
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