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  1. #1
    skate14's Avatar
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    1998 Jeep Cherokee Not Charging Battery

    Hello All, Have a 1998 Cherokee 4.0, need help with problem:

    Alternator is not send charge to battery, was intermittent now no charge at all.
    1. Replaced battery
    2. Replaced Alternator
    (even though they both tested good)
    3. PCM has been replaced

    Does anyone have a schematic for which harness from pcm the voltage regulator wiring to alternator is on?(ie black white or grey connectors to pcm)
    any and all help/suggestions would be GREATLY appreciated..Thanks

  2. #2
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    Re: 1998 Jeep Cherokee Not Charging Battery




    CAVCIRCUITFUNCTION1K72 18DG/ORGENERATOR FIELD SOURCE (+)2K20 18DGGENERATOR FIELD DRIVER3--4Z0 6BKGROUND

    CHARGING SYSTEM OPERATION

    The charging system consists of:
    • Generator
    • Electronic Voltage Regulator (EVR) circuitry within the Powertrain Control Module (PCM)
    • Ignition switch (refer to Ignition System for information)
    • Battery (refer to Battery for information)
    • Battery temperature sensor
    • Generator Lamp (if equipped)
    • Check Gauges Lamp (if equipped)
    • Voltmeter (refer to Instrument Panel and Gauges for information)
    • Wiring harness and connections (refer to Wiring for information)
    The charging system is turned on and off with the ignition switch. When the ignition switch is turned to the ON position, battery voltage from the powertrain control module (PCM) is supplied to the generator rotor to produce a magnetic field. This is done through one of the two field terminals at the rear of generator.
    The amount of DC current produced by the generator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is connected in series with the second rotor field terminal and ground.
    A battery temperature sensor, located in the battery tray housing, is used to sense battery temperature. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength of the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly.
    All vehicles are equipped with On-Board Diagnostics (OBD) All OBD-sensed systems, including EVR (field control) circuitry, are monitored by the PCM. Each monitored circuit is assigned a Diagnostic Trouble Code (DTC) The PCM will store a DTC in electronic memory for certain failures it detects. Refer to On-Board Diagnostics in Group 25, Emission Control System for more DTC information.
    The Check Gauges Lamp (if equipped) monitors: charging system voltage, engine coolant temperature and engine oil pressure. If an extreme condition is indicated, the lamp will be illuminated. This is done as reminder to check the three gauges. The signal to activate the lamp is sent via the CCD bus circuits. The lamp is located on the instrument panel. Refer to Instrument Panel and Gauges for additional information.

    CHARGING SYSTEM RESISTANCE TESTS

    These tests will show the amount of voltage drop across the generator output wire, from the generator output (B+) terminal to the battery positive post. They will also show the amount of voltage drop from the ground (-) terminal on the generator to the battery negative post. Typical generator wiring harnesses are shown in Generator Terminals (Typical Wiring Harness Shown) or Generator Terminals (Typical Wiring Harness Shown) Wiring harness routing as shown may be slightly different depending on vehicle model and/or engine. Refer to Wiring Diagrams for additional information.
    A voltmeter with a 0 - 18 volt DC scale should be used for these tests. By repositioning the voltmeter test leads, the point of high resistance (voltage drop) can easily be found.
    PREPARATION

    1. Before starting test, make sure battery is in good condition and is fully-charged. See Battery for more information.
    2. Check condition of battery cables at battery. Clean if necessary.
    3. Start the engine and allow it to reach normal operating temperature.
    4. Shut engine off.
    5. Connect an engine tachometer.
    6. Fully engage the parking brake.
    TEST

    1. Start engine.
    2. Place heater blower in high position.
    3. Turn on headlamps and place in high-beam position.
    4. Turn vehicle interior lamps on.
    5. Bring engine speed up to 2400 rpm and hold.
    6. Testing (+) circuitry:
      1. Touch the negative lead of voltmeter directly to battery positive post.
      2. Touch the positive lead of voltmeter to the B+ output terminal stud on the generator (not the terminal mounting nut) Voltage should be no higher than 0.6 volts. If voltage is higher than 0.6 volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.6 volts, look for dirty, loose or poor connection at this point. Also check condition of the generator output wire-to-battery bullet connector (if equipped) Refer to iring for connector location. A voltage drop test may be performed at each (+) connection in this circuit to locate the excessive resistance.
    7. Testing (-) circuitry:
      1. Touch the negative lead of voltmeter directly to battery negative post.
      2. Touch the positive lead of voltmeter to the ground terminal stud on the generator case (not the terminal mounting nut) Voltage should be no higher than 0.3 volts. If voltage is higher than 0.3 volts, touch test lead to terminal mounting stud nut and then to the wiring connector. If voltage is now below 0.3 volts, look for dirty, loose or poor connection at this point. A voltage drop test may be performed at each (-) connection in this circuit to locate the excessive resistance. This test can also be performed between the generator case and the engine. If test voltage is higher than 0.3 volts, check for corrosion at generator mounting points or loose generator mounting.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    thanks, this is exactly what i think i needed. Gonna get started and I'll post results

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    Re: 1998 Jeep Cherokee Not Charging Battery

    I can't find a fuseable link between my alternator and pdc?

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    Re: 1998 Jeep Cherokee Not Charging Battery

    It's got to be there..It looks exactly like a regular wire except that its more flexible like theres no wire in it. Trace that Bk/Gy wire from the alternator and there should be a splice there where the fusible link starts.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    I had a simular problem. My battery cables had corrossion on the connectors but it did not look like it did.

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    Re: 1998 Jeep Cherokee Not Charging Battery

    i found the fl, but really couldnt tell if bad. i assume its good because i can measure the battery voltage on it.

    Is there anyway to install a voltage regulator work-around?????

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    Re: 1998 Jeep Cherokee Not Charging Battery

    Does the voltage change when the engine is running?..Check under the battery for a Battery temp. sensor and let me know if there is one. It should be mounted on the battery tray with the sensor face up towards the bottom of the battery. Black plastic sensor.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    the voltage is the same running as pre-ignition, only drops when revving up or accessories turned on. definitely running off of battery only. there is a batt temp sensor, looks fairly clean and wires are securely connected.

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    Re: 1998 Jeep Cherokee Not Charging Battery

    With the volt meter monitoring the output voltage circuit on the generator, disconnect the battery temp sensor and see if the voltage changes, if not , run a jumper across the terminals going to the PCM and see if the voltage changes.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    i'll try that this morning.

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    Re: 1998 Jeep Cherokee Not Charging Battery

    no change in voltage either way

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    Re: 1998 Jeep Cherokee Not Charging Battery

    Swap the ASD relay for a known good relay. Wiggle the harness to the PDC and the PCM and see if theres any change.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    i swapped the relays around already and wiggled my tail off all around the harness

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    Re: 1998 Jeep Cherokee Not Charging Battery

    gonna get a check on the NEW alternator just to make sure. charging was intermittent, but now no charge at all. when i put new alt in it was charging fine then, nothing after a while.

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    Re: 1998 Jeep Cherokee Not Charging Battery

    found problem... was a cracked ring connector on ground from alternator to engine block. a very fine crack at base of ring was causing intermittent charging. additional problem was a faulty NEW alternator, it had a factory defect on rectifier. Thanks for all of the help. The circuit schematics helped me to find other worn wires and connectors that needed to be cleaned as well.

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    Re: 1998 Jeep Cherokee Not Charging Battery

    Huh? i lost all my hair for a broken ground connector?, J/k glad you found the culprit though.
    Confucious says: Don't eat the snow where the huskies go!

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    Re: 1998 Jeep Cherokee Not Charging Battery

    now arent those grounds fun

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    Re: 1998 Jeep Cherokee Not Charging Battery

    not fun at all, i believe this jeep is possessed. next item up is cleaning the neutral safety switch...what a joy i know that's going to be...ha,ha

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    Re: 1998 Jeep Cherokee Not Charging Battery

    did you check volt reg inside alt there known to be bad even new ones fail sometimes
    ALL I OWN ARE JEEPS!

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