Question about 1994 Mercury Cougar

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I installed new altenator but battery light stays lite and it will not charge

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  • jeffmarunde Jul 16, 2010

    new battery new alt just will not put out any voltage

  • jeffmarunde Jul 16, 2010

    had alternator checked and it is good

  • jeffmarunde Jul 16, 2010

    in the car

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2 Answers

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  • Master
  • 6,784 Answers

There seems to be a no charge state in this case. I recommend checking the charging system. Use the procedure below to isolate this issue.

Wear protective eye wear and clothing and remove all jewelry when checking your battery and charging system. Jewelry is a good conductor of electricity and is not recommended. Most batteries wear out every 3 to 5 years and need to be replaced. Always replace your battery with an equal replacement battery to assure proper operation. Automotive batteries have a positive terminal (red), negative terminal (black). Electricity is stored in the battery and then supplied to the vehicle when the engine is not running. While the engine is running the vehicles alternator charges the battery for future use. (Note: never disconnect the battery while the engine is running). To check a battery surface voltage, remove the positive terminal protective cover. Connect the positive side meter lead (red) to the positive side battery terminal. Connect the negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.5 and 12.8 volts.(You will need to use a voltmeter for this testing procedure). If the voltage is not up to specs, replace the battery asap. If the battery is ok and showing good voltage readings; Move on to the alternator drive belt and amperage test.

The alternator is rotated by a drive belt, which is, driven by the vehicles engine crank shaft pulley while it is running. Electrical voltage and amperage are generated to recharge the battery and supply voltage to the electrical system of the car. The alternator is held in place with mounting bolts. There is a main electrical wire on the rear of the alternator that supplies voltage to a main voltage junction box. If your alternator is not charging properly, your battery will slowly drain down from operating all the electrical systems in your car and stop the car from running. Most non charge states will be the cause of a loose belt or a low tension rate, due to a mis-adjusted alternator. Make sure you have enough tension in the belt for full rotation of the alternator pulley.

Next, you will need to check the alternators output with the Amp meter.

Testing the amperage output of an alternator is good for measuring the amount (not the level) of voltage the alternator can produce. This test can be tricky because if the alternator is weak it can still show it as producing amperage(False reading); Which is good, but if the voltage is low, it will still allow the battery to go dead. To check the amperage output of an alternator an amp meter will be required. Once the meter is connected start the engine. Next; Turn on all electrical accessories and raise the engine idle to about 1300 RPM. The alternator should produce the max amperage it was designed to produce. Example: a 90 amp alternator should produce about 88 amps. An alternator cannot sustain maximum output for long periods of time. If the alternator is forced to operate at maximum output it will overheat and fail(due to a failed regulator). An alternator is designed to operate at max amperage output only for a reasonable amount of time. Once you have verified the amp readings, check the voltage. To check the voltage, Connect the voltage meter lead the same way you would in a battery static voltage check, Start engine (do not drive). At engine idle, the voltage should be between 13.6 to 14.3 volts. If not the alternator may need replacing.


In conclusion; I suspect that the alternator was installed incorrectly. Check all connections and use the amperage and voltage tests to confirm proper connections. Also; make sure the drive belt is indeed turning the alt pulley will correct force. Check the tension rate to be sure the belt is tight, as stated above.

Posted on Jul 16, 2010

  • Michael Masters
    Michael Masters Jul 16, 2010


    • NOTE_ There is a mega or maxi fuse located in the power distribution box that will blow during an alternator failure. If it is not replaced before you install the new alternator, it will not allow the new alternator to charge. The battery light will stay on, as well. Check the alt maxi fuse under the hood; Replace it if found to be open(busted filament).


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  • Mercury Master
  • 6,826 Answers

Check that the alternator is getting current at the post with the thick wire that holds the cable end eyelet with a nut.

Use a test light to ground this post and see if it lights. If it does, then that part of the circuit is OK.

Have the battery charged and tested to make sure it is not shorted out.

Then, you might try having the alternator you installed tested while in the car with a starting charging computer at say Walmart or Sears or another garage.

They can detect if diodes are burnt out or if the voltage regulator is putting out enough current.

Sometimes new alternators, if they are not Lifetime warranted, will fail on the first try, in my experience.

So, I always get the lifetime warranty for alternators just to be sure.

Posted on Jul 16, 2010

  • 4 more comments 
  • Duane Wong
    Duane Wong Jul 16, 2010

    Sometimes there are 'quality' control issues in rebuilt alternators, where the alternator you get fresh out of the box is bad. That's why it should be tested again after it was installed in the vehicle.



  • Duane Wong
    Duane Wong Jul 16, 2010

    the battery light on your dash hooks directly to the alternator. If you have a red battery or charge light, then you have a problem with that alternator.



    Really.

  • Duane Wong
    Duane Wong Jul 16, 2010

    Was the alternator checked 'in' the car or 'out' of the car on a bench?

  • Duane Wong
    Duane Wong Jul 16, 2010

    Check if there is an external voltage regulator behind the battery:



    Voltage Regulator
    REMOVAL & INSTALLATION
    Electronic Regulator


    1. Remove the battery ground cable. On models with the regulator mounted behind the battery, it is necessary to remove the battery hold-down, and move the battery.
    2. Remove the regulator mounting screws.
    3. Disconnect the regulator from the wiring harness.
      To install:

    4. Mount the regulator to the regulator mounting plate. The radio suppression condenser mounts under one mounting screw; the ground lead under the other mounting screw. Tighten the mounting screws.
    5. If the battery was moved to gain access to the regulator, position the battery and install the hold-down. Connect the battery ground cable, and test the system for proper voltage regulation.

    Integral Regulator

    1. Disconect the battery ground cable.
    2. Remove the alternator from the engine as described previously.
    3. Remove the four screws retaining the regulator to the alternator rear housing. Remove the regulator, with brush holder attached, from the alternator.





      Fig. 1: Unfasten the retaining screws, then remove the regulator from the alternator housing



    4. If necessary, hold the regulator in one hand and break off the tab covering the, A marked, screw head with you hand or a prytool, if necessary.





      Fig. 2: Hold the regulator in one hand and break off the tab covering the, A-marked, screw head



    5. Remove two screws retaining the regulator to the brush holder. Separate the regulator from the brush holder.





      Fig. 3: Unfasten the two retaining screws, then separate the regulator from the brush holder

      To Install:

    6. Wipe the regulator base plate with a clean cloth, position the regulator against the brush holder and install the two retaining screws. Tighten the screws to 20–30 inch lbs. (2.3–3.4 Nm).
    7. Cover the head of the A terminal screw head with electrical tape.
    8. Locate brushes in brush holder and hold in place with a thin, flat piece of steel, rubber band or equivalent. Loop the brush leads toward the brush end of the brush holder.





      Fig. 4: Hold the brushes in place the brush holder with a rubber band, then position in the alternator housing



    9. Wipe the alternator rear housing with a clean cloth. Position the regulator and brush holder assembly in the alternator rear housing and pull the piece of steel or rubberband out.





      Fig. 5: Use a suitable tool to cut the rubber band, . . .






      Fig. 6: . . . then pull the rubber band from the alternator housing



    10. Install the regulator retaining screws and tighten to 25–35 inch lbs. (2.8–4.0 Nm).
    11. Install the alternator in the vehicle, then connect the negative battery cable.

  • Duane Wong
    Duane Wong Jul 16, 2010

    Sometimes the installer assumes the regulator is built in but it's not.

    Nowadays, it's rare to have an external voltage regulator, but on this car

    it might be that way. It's 16 years old.



    I remember cars from the 1980s and earlier had external voltage regulators

    made by the Ford Motor Company and Chrysler.

  • Duane Wong
    Duane Wong Jul 16, 2010

    No-Load Test


    1. Connect a tachometer to the engine.
      CAUTION
      Ensure that the transmission is in
      Park and the emergency brake is set. Blocking a wheel is optional and an added safety measure.


    2. Turn off all electrical loads (radio, blower motor, wipers, etc.)
    3. Start the engine and increase engine speed to approximately 1500 rpm.
    4. Measure the voltage reading at the battery with the engine holding a steady 1500 rpm. Voltage should have raised at least 0.5 volts, but no more than 2.5 volts.
    5. If the voltage does not go up more than 0.5 volts, the alternator is not charging. If the voltage goes up more than 2.5 volts, the alternator is overcharging.
      NOTE: Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.


    6. If the voltage is within specifications, proceed to the next test.

    Load Test

    1. With the engine running, turn on the blower motor and the high beams ( or other electrical accessories to place a load on the charging system).
    2. Increase and hold engine speed to 2000 rpm.
    3. Measure the voltage reading at the battery.
    4. The voltage should increase at least 0.5 volts from the voltage test. If the voltage does not meet specifications, the charging system is malfunctioning.
      NOTE: Usually under and overcharging is caused by a defective alternator, or its related parts (regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. Many automotive parts stores have alternator bench testers available for use by customers. An alternator bench test is the most definitive way to determine the condition of your alternator.

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