Question about 1991 Jeep Wrangler

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Alternator will not work properly

I have replaced it three times .but it will not put out the right voltage why?

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  • brklynboy187 Jan 22, 2009

    its reading 11.8 volts. and yes the battery is new the alternator is new what next?

  • brklynboy187 Jan 22, 2009

    the battery is fully charged and the reading from the alternator is the same as the battery about 11.8

  • brklynboy187 Jan 23, 2009

    hey i appreciate the response my dad is a mechanic..lol however he thinks it could be a computer what do you think? il also check the others.

  • brklynboy187 Jan 23, 2009

    what about the ecm ?could that be it?

  • Mark Egan May 11, 2010

    11.8 volts at idle, or 2000 RPM?

    If the battery is fully charged, the alternator will have less output, than if undercharged, where is could be as high as 14.8 volts (I believe the low is 12.6 volts, but don't remember for certain.).

    I also agree to check the belt, although this may be a serpentine belt.

    Are the alternators remanufactured, or are they junk yard rebuilds? And I agree with knowing where the voltage regulator is, and I think it's in the alternator too, but you need to check.


  • Mark Egan May 11, 2010

    What voltage is it putting out? Is your battery fully charged or partially charged?

    How are you measuring the voltage output of the alternator?


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I'm just thinking that if your dad is a mechanic, then have him disassemble the alternator and see if he can see anything wrong. Assuming you've wired up the alternator correctly, I am just suspect that there are no brushes in the alternator, or the regulator is bad.

Are you measuring alternator output at the alternator, or at the battery? If at the battery, and you don't have it wired correctly, then you will not see anything but battery voltage. If you check voltage at the alternator output, and it's higher than battery voltage, then there is something wrong in the wiring, either incorrectly wired, or a bad connection somewhere, as the voltage goes to the power distribution block.
Check that there is not a fuse for the alternator in the fuse panel. It may be the original alternator somehow caused a fuse to fail. It could be that there is no field power from the battery feeding the alternator through that circuit.

Posted on Jan 23, 2009

  • Mark Egan Jan 23, 2009

    ECM is unlikely. One way to tell for sure, go to a repository library and see if they have the factory service manuals (not Haines or Motors or Chiltons) for your specific vehicle. They usually have complete troubleshooting charts, wiring diagrams, everything you need that the dealers use.

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You might have them check and se that you are getting the right alternator.it could also be because of the battery not pushing enough volts back to the alternator that is keeping the reading off. have the battery tested and see if you have a dead cell or low reading on it

Posted on Jan 22, 2009

  • Ronnie Houston Jan 22, 2009

    is the voltage regulator inside the alternator on that vehicle? i cant remember right off if it is or not. does the belt have enough tension on it?

  • Ronnie Houston Jan 22, 2009

    you may need a bigger battery too i didnt think about that..cold cranking amps should be around 750 or so..

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The ECU has no control on the voltage. Does your vehicle have a separate voltage regulator? If so that's your fault. A lot of alternators have the regulator built into them. The alternator needs to be put on a test rig away from the vehicle and the output tested, this will eliminate the vehicle, You could disconnect the wiring to the alternator, run three fly leads to the alternator and to a separate battery and run the engine and test the voltage on the spare battery. Wire 1: Battery neg to case of alternator Wire 2: Battery pos to + terminal on alt (the thick wire) Wire 3: Battery pos through a 5 watt bulb to the ind terminal (ignition light) 17 volt will blow another battery for sure.

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My 2005 Pontiac Sunfire has had several problems over the past couple of months. When I was driving all my gages went to zero when I would start to break. After I started moving again they would go up....


Your car's symptoms (voltage fluctuations under load that shouldn't happen) seem to
strongly indicate that your voltage regulator has failed. The voltage regulator is the component
that regulates voltage coming from the alternator, and which is supplied to the rest of the car.
Your new belt tensioner indicates to me (and should have to your mechanic) that the
alternator and/or voltage regulator weren't able to operate properly, and a faulty belt tensioner
has killed more than one car's alternator/voltage regulator.
Your do not need new headlights. Do fix the turn signals.

In the 2005 Sunfire, the voltage regulator is an integral component of the alternator, and is
not separately serviceable. So your 2005 Sunfire needs a new alternator.

2005 Pontiac Sunfire Alternator - Duralast Part Number: DL2305-15-4 $199.99 available at:
http://www.autozone.com/autozone/parts/2005-Pontiac-Sunfire/Alternator/_/N-jmqtpZ93xme

The national parts chains (Advance Auto Parts, AutoZone, Pep Boys) will (for free) administer
a "Charging System Test." Which will telly you for sure that your alternator/voltage regulator
is bad. Do this before replacing alternator, since its a pricy part in the 05 Sunfire.

Just in case, Here's the 2005 Sunfire manual entry on (a) Diagnosis & testing the alternator, and
(b) replacement of the alternator

Alternator replacement is a do-it-yourself project, though you may need to get a
"Serpentine Belt Kit" on your favorite parts store's loan-a-tool program to remove/re-install the serpentine (drive) belt.
======================================================================
Diagnosis & Testing - 2005 Pontiac Sunfire Alternator


Alternator 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 (voltage regulator), and replacement will fix the problem; however, faulty wiring and other problems can cause the charging system to malfunction. 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.




Alternator 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. 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.



Voltage Test

1. Make sure the engine is OFF , and turn the headlights on for 15-20 seconds to remove any surface charge from the battery.

2. Using a DVOM set to volts DC, probe across the battery terminals.

3. Measure the battery voltage.

4. Write down the voltage reading and proceed to the next test.



Removal & Installation - 2005 Pontiac Sunfire Alternator


2.2L (VIN 4) Engines

1. Before servicing the vehicle, refer to the precautions section.

2. Remove or disconnect the following:

Negative battery cable

Accessory drive belt

Alternator mounting bolts

Alternator electrical connectors

Alternator





To install:

1. Before servicing the vehicle, refer to the precautions section.

Alternator. Torque the upper bolts to 37 ft. lbs. (50 Nm) and the lower bolt to 22 ft. lbs. (30 Nm).

Alternator electrical connectors

Accessory drive belt

Negative battery cable





2.2L (VIN F) Engines

1. Before servicing the vehicle, refer to the precautions section.

2. Remove or disconnect the following:

Negative battery cable

Accessory drive belt

Alternator mounting bolts

Alternator electrical connectors

Alternator





To install:

1. Install or connect the following:

Alternator. Torque the bolts to 16 ft. lbs. (22 Nm).

Alternator electrical connectors

Accessory drive belt

Negative battery cable

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3 Answers

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