Question about 1965 Ford Mustang

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Alternator light on

Have 65 Mustang with 289. Alternator light stays on constant. Battery is good, have replaced alternator and voltage regulator. Engine shuts off immediately when battery cable disconnected. Any help on what to look for next??

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  • Anonymous Mar 30, 2014

    Replaced the alternator and battery and battery light is still on, even though battery was out of the car for more than a day. Obviously, disconnecting the battery did not solve the problem. Any other suggestions?

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The alternator is not producing any power . If it were the engine would run without the battery. Check the wiring on the alternator. It must ave an exciter wire to make it work.

Posted on Oct 07, 2008

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Why does the battery warning light stay on while driving


The battery warning light is triggered by the alternator internally. The alternator may be charging properly, however, the internal voltage regulator inside the alternator may have a problem resulting for the light to illuminate. There may be also a wiring issue from the alternator to the light causing the problem as well

Jan 15, 2016 | 2001 Oldsmobile Alero

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Number ten fuse keeps popping its for the battery voltage sensor alternater good battery good starter good and battery light stays on plz help


Sounds like a voltage regulator. You never said what type of car it was. Some vehicles have voltage regulators that are built into the alternator..other models the regulator can be separate. If it is part of the alternator the whole alternator will need to be replaced. If it is a separate component it may be a matter of buying a new regulator (plug and play). Have your vehicle load tested at a reputable auto service first.

Aug 05, 2015 | Cars & Trucks

1 Answer

2003 bmw x5 4.4 battery light stays on


Brother Mark, changing the battery with a new one being done won't make the light go out, as you noticed. Light is still on so you changed the alternator. Good, but the battery light is STILL on. This only means that the charging circuit from the alternator is not working in the voltage regulator or the wiring is not connected properly to the alternator/regulator. A new battery will show over 13 to 13.5 volts not connected. An old battery will still show 12 volts and still be weak or bad. After connected and engine running, the system will show at least 14 volts because alternator/regulator is working properly, using a voltmeter/load tester connected to the battery. If after replacing the battery and alternator it is still reading 12 to 13.5 volts, it is not working and the light will stay lit on the dash. You may have purchased a faulty alternator if the system tests out this way. Have your system checked with a volt meter or load tester bit be sure all the connections are proper and clean.

Mar 26, 2014 | BMW X5 Cars & Trucks

2 Answers

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).

Next, disconnect the voltage regultor harness plug from the alternator and check the voltage at the wiring harness regulator plug's "A" terminal connector - the yellow/white wire. It too should be full battery voltage. If it is anything less than full battery voltage, you must determine why. In this case, look at the 20-amp ALT fuse in the battery junction box, and at the various splices and connectors in that circuit.

Then, turn the key switch to its "RUN" position and measure the voltage
at the wiring harness regulator plug's "I" terminal connector - the light green/red wire. It should be somewhere between 8 and 12 volts. If there is no voltage present, check Fuse 5 (15 amps) in the main fuse panel and the various connections in that circuit.

The final test is to measure the voltage between the batterty positive terminal and the alternator housing or frame. If it is anything less than full battery voltage, check the alternator mounting.


7_19_2012_12_45_20_pm.jpg

Jul 19, 2012 | 2000 Ford Mustang

1 Answer

2003 mustang gt drains battery in 2 days


03 Mustang GT (Parasitic) Battery Drain Fix
welcome.gif
Hello,
I am seeing a lot of mustangs are having battery draining issues and I wish to share some simple solutions found while working on a friends 03 GT 4.6ltr.

In a quiet area, key switched off, hood up, Listen carefully close to alternator. I heard a high pitched hissing/whistle sound at low volume, came from back of alternator. This sound was the voltage regulator/rectifier staying on when key is off due to faulty diodes inside the voltage regulator/rectifier circuit, can cause battery to go dead after car not ran in about 2-7 days.

After having the alternator tested free at a parts store, test showed alternator was good because the faulty diodes in the alternator did not show up on the test, the machine did not test for faulty drain back issues that were present.
Alternator on-car-fix:

There was battery voltage running at all times through the two-wire connector on back of alternator. Disconnect the battery first for safety and to reduce chance of short circuit. The yellow wire/with white stripe is hot while car is off so I traced this from the 2-wire connector on the alternator then closer towards driver side front fender. Next I cut the Yellow/White Stripe wire, spliced a good connection wire to it and ran it through a hole in the fire-wall to the fusebox(under dash), connected it to a 15a fuse that does not get used but has power when key is turned on but no power when key is off.

The purpose for re-routing the hot wire to the alternator, is to turn off the alternator charging circuit when the key is turned off so it may not run down the battery. I am seeing good results with this fix(or patch) so far. No More Parasitic Battery Drain!

Another fix can be to change the small pulley on the alternator to a larger pulley so the alternator does not spin too fast, putting too much energy through the diodes can cause a charging system to act a fool. So if you have charging issues and have an alternator changed, putting a larger pulley on can make sense turn into saved dollars(especially on high revving engines).

I hope this info helps to solve some draining battery and/or alternator issues.

thanks.gif for reading,

TyBorg1

Apr 12, 2012 | 2003 Ford Mustang

1 Answer

I have a 2002 mitsubushi montero sport. The brake/battery light won't go off. I replaced the battery yesterday and car starts and stays running but lights seem a little dim and the dang brake/battery...


CHECK ALTERNATOR DRIVE BELT COULD BE LOOSE NEED ADJUSTING OR GLAZED NEED REPLACING. IF ALL IS GOOD, CHECK ALTERNATOR VOLTAGE OUT PUT AT BATTERY SHOULD BE 13.5 - 14.5 VOLTS. IF NOT ALTERNATOR FAULTY BUT CHECK ALTERNATOR BATTERY FEED AND VOLTAGE REGULATOR WIRES FOR LOOSE CONNECTION OR DAMAGED FRAYED WIRES. CHECK ALTERNATOR FUSE.CHECK THOSE THINGS BEFORE BUYING NEW ALTERNATOR.FIRST TURN OFF RADIO BEFORE DISCONNECTING BATTERY CABLE TO KEEP FROM LOCKING OUT RADIO.

Aug 05, 2011 | 2002 Mitsubishi Montero Sport

2 Answers

I have a 1999 3,8L ford mustang my tester indecates the alt is overcharging,but the batt light is coming on but it goes off! is there anything i can do to besides replace the alt?


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
voltage regulator is an integral component of the alternator.

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

archaeology_70.jpg


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


archaeology_71.jpg

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

archaeology_72.jpg



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

archaeology_73.jpg


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

archaeology_74.jpg


=========================================================
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

archaeology_75.jpg


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

archaeology_76.jpg



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.

Jul 07, 2011 | 1999 Ford Mustang Cobra

1 Answer

Battery light randomly comes on


Sounds like the voltage regulator is starting to fail. Your voltage regulator is built in to the alternator, so you should replace your alternator before it dies completely and leaves you stranded somewhere.

May 24, 2009 | 2006 Ford Mustang

1 Answer

65 mustang alternator problem


The only other thing may be the voltage regulator, is this actually an alternator or a generator?

Oct 08, 2008 | 1965 Ford Mustang

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