Question about 1981 Ford F 100

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Wiring Motorcraft alternator internal regulator What does terminal D+ require is it switched 12 volts or something else

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Posted on Jan 02, 2017

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SOURCE: alternator not charging


If you have a volt meter, set it to volts and hold the negative probe to the alternator body and the positive to the battery positive. If you don't get battery voltage then the alternator isn't grounded and the probable cause is the main engine ground cable either breaking or coming loose.

Very best regards


Posted on Jun 10, 2008

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SOURCE: home wind generator early model chev alternator need schematic

Ok I'm going to try this from memory...last time used it was a few years back when wiring up a big boat. Large (B+) wire goes from battery to large terminal on alternator back. Facing the rear of the alternator, top spade connector on alt goes to a switch (there was supposed to be a resistor in that wire, but I never used one) switch connects to (+) on battery. Terminal on right goes to the (B+) terminal on alternator. Alt case is ground.
I can't find my old chiltons electrical book but that is how I remember it.

Posted on Apr 07, 2009

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SOURCE: Chevy G20 1985 wiring (charging problem)

Posted on Jul 08, 2009

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SOURCE: wiring an amp meter diagram

put the meter in series remove wire gointo back of alternator put one lead on wire and one on alternator that should give you your reading

Posted on Jul 23, 2009

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SOURCE: wiring ??? I'm installing dual 12 volt battery's

pos to pos and neg to neg for 12 volt but if your system is 24 volt thats a different story it will be pos to neg.and pos to neg

Posted on Nov 02, 2009

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Replaced alternator 3 times and battery 2 times and still getting various readings from alternator voltage on a 2006 mitsubishi galant 4 cycindler ?

depending on the variations
after starting or cranking for a while the voltage will read 14.5 to 14.8 volts as the battery charges up that reading will drop back to 13.2 volts
it will be lower at idle 12 >13 volts as the alternator speed has to be around 1,500 rpms to get the alternator to charge
using the lights and any extra power requirements the voltage will go up to max of 14.5 -14.8 volts to compensate for the extra current required
drive belt condition and tension will cause variations if it is not correct
bad connections ( dirty terminals , loose harness fittings , corrosion) will all affect the ability of the alternator /regulator to produce constant voltage
you will have to ask an auto electrician if the regulator is part of the ECM as most have the regulator in the alternator or a separate unit on the fire wall
If it not part of the ECM then the ECM will have no bearing on the readings

Dec 05, 2016 | 2006 Mitsubishi Galant

2 Answers

The battery on my rhino loses volts when driving .battery dies then i have to boost it..something is drawing on the battery when the key is off ?????????

If the battery is not being properly charged while unit is running, it will go dead. You may have a problem with the voltage regulator or magneto causing the no charge issue

Mar 10, 2016 | Cars & Trucks

1 Answer

What is causing the battery to drain?

Running the car will drain the battery it if it's not charging ! An if your charging light is on it isn't charging ! Did you check power an grounds on the alternator ? There is a single heavier wire on the back of the alternator, this should have battery voltage ! You may want to take this to a ASE certified repair shop !
With the ignition switch in the RUN position, voltage is applied through the warning indicator I circuit 904 (LG/RD) to the voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit 35 (OG/LB) to the generator field coil. When the engine is started, the generator begins to generate alternating current (AC) which is internally converted to direct current (DC). This current is then supplied to the vehicle's electrical system through the output (B+) terminal of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the regulator S circuit 4 (WH/BK). This voltage feedback signal (typically half the battery voltage) is used to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the A circuit 35 (OG/LB). The A circuit 35 (OG/LB) voltage is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain the correct generator output.
The set voltage will vary with temperature and is typically higher in cold temperatures and lower in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.
Battery Positive Output (B+) Circuit 38 (BK/OG)
The generator output is supplied through the battery positive output (B+) terminal on the back of the generator to the battery and electrical system.
I Circuit 904 (LG/RD)
The I (ignition) circuit 904 (LG/RD) is used to turn on the voltage regulator. This circuit is powered up with the ignition switch in the RUN position. This circuit is also used to turn the charging system warning indicator on if there is a fault in the charging system operation.
A Circuit 35 (OG/LB)
The A (battery sense) circuit 35 (OG/LB) is used to sense battery voltage. This voltage is used by the regulator to determine generator output. This circuit is used to supply current to the generator field (rotor). The amount of current supplied to the rotor will determine generator output.
S Circuit 4 (WH/BK)
The S (stator) circuit 4 (WH/BK) is used to feed back a voltage signal from the generator to the regulator. This voltage is used by the regulator to turn off the charging system warning indicator. The S circuit is fed back externally on external mounted regulator generators.
Visual Inspection Chart Mechanical Electrical
  • Battery case, posts, hold-down clamp, cables and connections
  • Generator drive (serpentine) belt for condition and tension to make sure there is no slip between the belt and the pulley. For additional information, refer to Section 303-05 .
  • Battery charge
  • Generator pulley
  • Battery junction box (BJB)Mega Fuse
  • Battery junction box fuse:
    • 11 (20A)
  • Central junction box (CJB) fuse:
    • 30 (30A)
  • Circuitry
  • Charging system warning indicator
  • Cables
  1. Check the operation of the charging system warning indicator lamp (instrument cluster). Normal operation is as follows:
    • With the ignition switch OFF, the charging system warning indicator should be OFF.
    • With the ignition switch in RUN and the engine off, the charging system warning indicator light should be on.
    • With the engine running, the charging system warning indicator light should be off.
  1. Verify the battery condition. Refer to Section 414-01 .
Normal Charging System Voltages and Charging System Warning Indicator Operation Ignition Switch Position A Circuit 35 (OG/LB) S Circuit 4 (WH/BK) I Circuit 904 (LG/RD) Generator B+ Circuit 38 (BK/OG) Battery Engine to Battery Ground Charging System Warning Indicator Operation OFF 12 volts 0 volts 0 volts 12 volts 12 volts 0 volts Off RUN-engine off 12 volts 0 volts 1-3 volts 12 volts 12 volts 0 volts Illuminated RUN-engine running 13-
15 volts 1/2 battery voltage 13-
15 volts 13-
15 volts 13-
15 volts 0 volts Off
  1. If the customer concern is verified after the initial inspection, refer to the Symptom Chart to determine which tests to carry out.
    • The charging system warning indicator is on with the engine running (the system voltage does not increase)
    • Circuitry.
    • Voltage regulator.
    • Generator.
    • GO to Pinpoint Test B .
    Your whole problem is the alternator is not charging , a couple tests with a volt meter would tell you !

Aug 16, 2015 | 2001 Ford Expedition

1 Answer

Alternator Wiring Diagram

Usually the alternators possess one thick white colored wire directly coming out of the battery positive terminal (+) which is around 8 mm (outer diameter) and connects the battery with alternator and white or black 3 wires connector which is inserted at the rear of the alternator. If you look carefully at the rear of the alternator you will find the embossed letters there. Some time the letter may vary depending upon model year of the vehicle. Normally the letters describe L= Alternator warning LAMP in the in the instrument panel of the speedometer. B= 12 Volts coming out of the ignition switch on the ON position. G= Ground or chassis ground.

Nov 25, 2013 | Toyota Land Cruiser Cars & Trucks

2 Answers

There is a ground some were that is causeing the battery not to charge put new selinoid ,new battery,alternater,new key lock cylender check wirers fuses relay switches and battery still wont charge

It sounds like you have done a whole lot of replacing and not much "diagnosing". Did you chech for battery voltage at the alternator? There should be battey voltage at the large Black/Orange wire that is on the B+ terminal of the alternator. This wire should have voltage all the time. If there is no battery voltage, you most likely have a burned fusible link at the starter relay area.
There should also be voltage at the "S" terminal with the ignition on. If there is no voltage, then check for voltage at the "S" terminal of the voltage regulator. If there is no voltage at the "S" terminal on the voltage regulator then check the "I" terminal on the regulator for voltage.

NOTE: The voltage on the "S" terminal should be 1/2 that of the voltage on the "I" terminal.

If there is voltage on the "I" terminal, make sure your voltage regulator is grounded properly to the fender and retest to see if it is charging the battery. If it is still not charging, disconnect the regulator connector and connect a jumper between the "A" and "F" terminals of the connector. Start the engine. The alternator should now be charging the battery at high voltage (usually over 15 volts) If it does, replace your voltage regulator. If it does not, then you need to check your wiring between the voltage regulator and the alternator.

Please also review this article:

What Else Could Be Wrong?

Jun 15, 2011 | 1987 Ford F 150

1 Answer

Alternator replaced


The different engine applications that the Ford Taurus and Mercury Sable are equipped with utilize different types of alternators. The following is a list of vehicle applications. For 1986-90 vehicles:

The 3.0L and the 3.8L engines utilize a side terminal alternator.

The 2.5L and the 3.8L (with Police Package only) engines utilize an alternator with an integral rear mount regulator and an internal fan.

The 3.0L SHO engines utilize an alternator with an internal fan and regulator.For 1991-93 vehicles:

The 2.5L, 3.0L and 3.8L engines utilize an alternator with a rear mount regulator and an internal fan.

The 3.0L and 3.2L SHO engines utilize an alternator with an internal regulator and fan.For 1994-95 vehicles:

The 3.0L, 3.8L and 3.0L SHO engines utilize an alternator with a rear mount regulator and an internal fan.

The 3.2L SHO vehicles utilize an alternator with a internal regulator and fan.

1. Disconnect the negative battery cable.
2. Loosen the alternator pivot bolt, then remove the adjusting bolt.
3. Remove the alternator drive belt from the drive pulley.
4. Tag and disengage the wiring terminals from the back of the alternator. The stator and the field wiring are the push-on type of retainer. After depressing the lock tab, the connector should be pulled straight off of the terminal to prevent damage.
5. Remove the alternator pivot bolt, then remove the alternator from the engine.
6. Position the alternator on the engine.
7. Install the alternator pivot bolt and the adjusting bolt, but do NOT tighten the bolts until the drive belt it tensioned.
8. Engage the wiring terminals to the alternator, as tagged during removal.
9. Install the drive belt over the alternator drive pulley, then adjust the belt tension using Belt Tension Gauge 021-00019, or equivalent.

When adjusting belt tension, apply pressure on the front housing only.

10. Tighten the adjusting bolt to 30-45 ft. lbs. (41-61 Nm), then tighten the pivot bolt to 50-70 ft. lbs. (68-94 Nm).
11. Connect the negative battery cable.

Hope helps.

Jan 07, 2011 | 1990 Ford Taurus

1 Answer

Batterie light stays on after changing alternator

The yellow wire in your Alternator plug Have a "Fuse Link" at the starter relay. If that fuse link is bad the alternator will not charge. To test jump the yellow wire with the hot wire at the alternator and if the alternator is new it should charge. Check and install the fuse links.

Other details that you can try:
First ensure your battery terminals are clean and free of corrosion. Make sure you use a battery tool to clean them up to ensure a good connection. reconnect and tighten.

NOTE: Some electrical systems need to have the system computer reset after changing an alternator. If you changed the battery first, then changed the alternator, this may not have happened. Sometimes it's as easy as fully disconnecting both terminals and reconnecting the battery.
Check the voltage from the positive terminal of the battery to the negative terminal on the battery(record this).

Then check voltage from the positive terminal of the battery to where the negative terminal connects to the block. if this reading is lower your negative battery cable may be the problem. I've had them crystallize before from age so badly that they lost flexibility and began breaking internally. Replace it.

Then check voltage from the smaller positive cable post on the alternator and the negative terminal on the battery. If this is lower the smaller cable may be the problem. Replace it.

Then check voltage from where your positive cable hooks up to the solenoid and to the negative terminal on the battery. if this is lower your positive battery cable may be the problem. Replace it.

Charge the battery fully and take the vehicle to a local auto parts store and see if they can run a charging system test (usually a free service). They should be able to tell you what kind of shape your battery is in and the alternator output. A good alternator will put out 14+ volts, if it's putting out 12-14 volts it's wearing out and needs replaced.

If your alternator is putting out 10-10.5 volts or less means one of the diode pairs are bad, 5-5.25 volts or less 2 diode pairs are bad. Either way the alternator is not charging the battery and it's the fault of the voltage regulator.

Ask the person doing the test if he can tell you what the field voltage is on the alternator. If they can and it is around 12 volts or more you can probably bypass the next test.

Start the vehicle and hold a steel tool near the back of the alternator (not on the pulley side). It should be drawn magnetically to the center of the alternator. If it doesn't your alternator is not generating the magnetic field needed, to generate electricity. This could be due to a bad alternator or wiring.

WARNING: The next test is the "old fashioned" way we shade-tree mechanics used to do this. It can be done with the engine running in most cases, but you must be extremely careful that you don't get clothing or long hair anywhere near the pulleys. You do this at your own risk. If you are uncomfortable with taking such a risk, have your mechanic look into it. Disconnect the two wire box-like electrical connector from the alternator's voltage regulator and see if there is any voltage (should be around 12 or more volts DC) from the wires going to the alternator. You can try testing this with the engine shut down and the key on, but it may not work on all vehicles.

With connector disconnected, if the voltage is less than 12volts or non-existent, it's a wiring problem. - With connector disconnected, if it is 12 volts or above it's probably the alternator (Bad windings.)
Set the multimeter to Ohms. Touch probes together and calibrate the needle to zero on right side of meter readout. (If the needle does not move to the right, you may need to replace the meter's battery or fuse). With the Alternator connector disconnected check the resistance of the alternator at the connector blades. If the needle goes to infinity, there is an open circuit in the windings. Replace the alternator.

Other things that can cause charging system problems:

  • Excessive starter draw - Remove starter and take to parts store for testing
  • Bad solenoid
  • Failed engine compartment fuses or resisters - Look for and check big rectangular ceramic ones as well on antique/classic vehicles
  • Failed fusible links
  • Failing ignition switch - Usually under the dash, Not at the key
  • Wiring to the key assembly inside the steering column - or on the dash older vehicles
  • Bad computer modules
  • Electrical wiring - This one takes the longest to isolate
  • Particularly hot wires arcing to ground
  • Some other Windstar threads suggest checking wiring bundles under the rubber boots at door hinges.
  • Other unassociated electrical components shorting to ground and placing a drain on the system - could be anything from a cigarette lighter, to lighting, to electric radiator fans failing to shut off, ignition coil, radio, sensor probes shorting to ground, etc. etc
Hope this help (remember rated and comment this).

Mar 19, 2010 | 2000 Ford Windstar

3 Answers

How to check truck altornator

start engine unhook positive cable if it dies its bad alternator or fuesable link between batt and alternator also a volt meter will tell u if its charging a good alternator will charge 13.50 to 14 volts

Mar 18, 2010 | 1988 Chevrolet C1500

2 Answers

Dead battery. Alternator is charging, but the juice is not getting to battery. 1998 Slk 230. There is a relay p/n 002 542 20 19 05 3905 00, by the battery, (G) from the alternator has 19.8 volts, battery...

19.8 volts is too high. the alt regulator is not working. The regulator needs a battery source feed to work. Both the feed for the regulator and the connection between the output post and the positive battery terminal should go through an ALT fuse. Start by checking that.

Feb 28, 2009 | 1999 Mercedes-Benz M-Class

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