Question about 1992 Ford Mustang

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1992 4cyl Mustang LX won't hold voltage.

I have replaced both the battery and the alternator twice, as well as the alternator plug. I have also checked both battery cables and replaced the negative terminal. I have checked the fuses. It starts right up, as long as the battery is new, or fully re-charged. With the new battery in place, the very first time I start it, it still only reads app. 9.5-10 volts. I can drive it that way, but it obviously doesn't last long as the voltage continues to drain off. Somewhere it is not charging, but where does an extreme novice start to look?

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Try the ignition switch. my thunderbird had the same problem.with it runing it was only charging at 11 volts.just look under 1991 thunderbird not charging or go to will tell you how to test it with a dmm or test light. dmm=digital multi meter.

Posted on Dec 11, 2008

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When you start the car does your stater ound like it is dragging ( slow turning )?,I would remove the starter and bench test it to see if it is dragging or operating properly. if you are not sure on doing this yourself look in the phone book for a shop that specializesin starters and altenators as they will usually test them for free, hoping to get your buisness and they can test it rite in the car without removeing it. I am thinking that your starter solonoid is shorting out and drawing your power. I am also wondering if your altenator belt is tight enough. also you mentioned that you checked and replaced one of your battery cables. was this because it was corroded inside ( under the insulation )?
good luck and I hope that this helps you, and remember to rate all the solutions that are posted to you.

Posted on Oct 18, 2008


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My daughter 2004 Kia won't hold a battery charge.

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99 mustang battery not charging

First off, disconnecting athe battery while the engine is running is the quickest way to damage an alternator. Unlike the old DC generators, the alternator needs the battery in circuit to protect it against voltage runaway.

If the alternator has been bench-tested and seems to be functional, I would start by verifying the related vehicle circuits. Witch a DC voltmeter, start out by measuring the voltage at the alternator's output terminal, the heavy black/orange wire. It should be full battery voltage. If it is anything less than battery voltage, you must determine why. Some things to look at are the gray 12-gauge fusible links A & B, and the various splices and connections in the circuit (see diagram below).

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Your alternator-mounted voltage regulator has failed. Luckily, your voltage regulator is
replaceable separately from the alternator (most voltage regulators are integral to the alternator,
and cannot be separately serviced).

Note: this works for 3.8L cobra alternators/voltage regulators only - in the 4.6L model, the
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1999 Ford Mustang Cobra -3.8L engine

3.8L Engines

1. Disconnect the negative battery cable.

2. Remove 4 Torx® head screws holding the voltage regulator to the alternator rear housing. Remove the regulator, with the brush and terminal holder attached.

Fig. 1. The regulator and brush/terminal holder are mounted on the backside of the alternator


Fig. 2. The regulator and brush/terminal holder are secured by 4 Torx® head machine screws


Fig. 3. Hold the regulator while removing the screws to prevent the regulator from dropping out and damaging the brushes


3. Hold the regulator in one hand and pry off the cap covering the A terminal screw head with a small prybar.

4. Remove 2 Torx® head screws retaining the regulator to the brush holder. Separate the regulator from the brush holder.

Fig. 4. Slide the regulator out-the brushes will move out of the holder


Fig. 5. The brush and terminal holder can be separated from the regulator once it is removed from the alternator


To install:

1. Install the brush holder on the regulator with 2 retaining screws. Tighten the screws to 25-35 inch lbs. (2.8-4.0 Nm).

2. Install the cap on the head of the A terminal screw.

3. Depress the brushes into the holder and hold the brushes in position by inserting a standard size paper clip, or equivalent tool, through both the location hole in the regulator and through the holes in the brushes.

Fig. 6. When installing the regulator, press the brushes back into the housing


Fig. 7. Use a thin piece of soft material, like this plastic wire tie, to hold the brushes in position while replacing the regulator, or use a paper clip inserted in the hole


4. Install the regulator/brush holder assembly and remove the paper clip. Install the attaching screws and tighten to 20-30 inch lbs. (2.3-3.4 Nm).

5. Connect the negative battery cable.

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