This is not a car question. I have a boat (Ford Escort Diesel engine) that uses a separate voltage regulator. My alternator has not been charging properly and there is a 5 amp drain in my system that I can't find. When I disconnect and then reconnect the vr the drain goes away until I turn on the ignition. I tested the vr and here is what I got. Ingition OFF - Red wire 12.17v, Brown and Blue wires 0v; Ignition ON but motor not running - Red wire 4v, Brown wire 4.25v, Blue wire 3.71v; Engine running - Red wire 3.03v, Brown wire 2.90v, Blue wire 2.36v. According to the wiring diagram - Red=power supply, brown=Ignition, Blue=Field. Is the vr bad? It is a Napa VR 428.

How old is the battery? In general, vehicle batteries are considered 'old' after 5 years especially on bigger engines.
Using a volt meter or a multimeter set to Volts try this. With the engine off and the Keys out test the voltage directly on the battery. You should get a reading somewhere around 12.6 to 13.2 volts. Start the engine and retest the battery voltage. If the alternator is working correctly the reading should rise to somewhere around 13.6 to 14.2 volts.

The voltage regulator in side the alternator could be starting to fail , transistors ! New alternator .

The voltage regulator type depends on which alternator you have (there are 2 different ones), on one the regulator is attached to the outside of the alternator and the other it is separate and mounted on the firewall I think. See pictures below so you can ID what you have.

Several things to check. Check alternator drive belt tension, check alternator voltage output, with the engine running at fast idle connect a volt meter across the battery terminals, around 13 to14 volts is ok. check if there is a light on in the glove box or boot. how old is the battery is holding a charge .

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




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




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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.

You have an electrical problem. That is for sure. The battery is down and is not being charged. Here are the things that cause it. And the things that don't. It does not seem like the battery is causing it, but the battery can be damaged by electrical issues. In Ford vehicles that I have had experience with, the alternator is separate from the voltage regulator. The voltage regulator controls how much electricity is used to charge the battery and how much is going into the electrical system of the car. If the voltage regulator is separate, then it can be purchased inexpensively from an auto parts place. Say less than $20.00. It will be mounted near the battery on a side wall. My guess is one or more of the diodes (one way electrical valves used to convert the alternating current generated from the alternator into DC current to operate the electrical system of the car and charge the battery, which is itself DC) in it have failed. The other twist in this is that the electrical system may have been redesigned to integrate the voltage regulator into the case of the alternator. If that is the issue, the alternator can be replaced, or if there is a skilled person that does rebuilds in your area, he will know how to change the diodes in the voltage regulating section of the alternator. You can save money this way. If you have a volt meter or a multimeter. Commonly around $25.00 these days, you should get a reading of around 12 volts from the battery when it is charged and the engine is off. If the battery is down, the voltage should still be in that area, but not enough kick behind it to do anything but light a small bulb. When the car is started and the voltage regulator is doing it's job you should get at least 13.5 volts DC at the battery terminals.

Many of the symptoms that occur also happen because of poor electrical contact at the battery.
Use Baking soda and water to clean the terminals of the battery of corrosion. And then use a battery cleaning tool for the battery posts and the battery wire clamps that go around the post. Make sure all of the connectors and wiring is sound.

I would then test all of this doing the following steps..

Charge up the battery.

Then connect the system and do the voltage checks. If the Battery is charging properly, the regulator will gradually reduce the charging voltage it is using to charge.

After 15 minutes, shut the engine down and check the battery voltage. and turn on the headlights to see if they are still bright.

If the voltage is at 12 volts DC the battery will live. If you are not getting enough charging voltage, which I believe is the situation then the voltage will constantly be to low at the battery. It will be the battery running the car and the bulbs and other things will go lower and lower.

One very simple test of a charging system is to charge the battery, start the engine, then pull the positive terminal off of the battery. If the engine dies, then the voltage being generated from the alternator is too weak.

Hope all of this helps,
Best,
Mark

IDENTIFICATION

There are 4 different types of alternators found on the years and model ranges covered in this information:

1. Rear Terminal, External Regulator, External Fan Alternator
2. Side Terminal, Internal Regulator, External Fan Alternator
3. Leece-Neville 165 Ampere Alternator
4. Integral Rear Mount Regulator, Internal Fan Alternator

Rear Terminal, External Regulator, External Fan Alternator
This unit utilizes a separate, external electronic regulator. The regulator is non-adjustable. The rear terminal alternator was standard equipment on 1987 trucks, and can be found on some 1992 motor home chassis models equipped with the 7.3L diesel or 7.5L gasoline engine.
Side Terminal, Internal Regulator, External Fan Alternator
This unit was optional on 1987, standard on all 1988-92 models and standard on 1993-96 models equipped with the 4.9L and 7.5L engines. The regulator in integrated within the alternator body and is not adjustable.
Integral Rear Mount Regulator, Internal Fan Alternator
This alternator is standard equipment on all 1993-96 models equipped with 5.0L, 5.8L gasoline engines and 7.3L diesel engines (except the 1996 F-Super Duty models).
Leece-Neville 165 Ampere Alternator
This unit is optional equipment on some 1989-94 trucks and ambulance packages. A separate, electronic, fully adjustable regulator is employed in this system.
Mitsubishi 215 Ampere Alternator
This unit is found on 1996 F-Super Duty models equipped with the 7.3L diesel engine. The regulator is integral and the fan is external.

REMOVAL & INSTALLATION

See Figures 1, 2, 3 and 4

Fig. Fig. 1: Disengage all wiring harness connections from the alternator

Fig. Fig. 2: Once it is unbolted, maneuver the alternator from the engine compartment

Fig. Fig. 3: Side terminal alternator

Fig. Fig. 4: Rear terminal alternator

1. Disconnect the battery ground cable.
2. Remove the adjusting arm bolt.
3. Remove the alternator through-bolt. Remove the drive belt from the alternator pulley and lower the alternator.

Some engines are equipped with a ribbed, K-section belt and automatic tensioner. A suitable tool must be made to remove the tension from the tensioner arm. Loosen the idler pulley pivot and adjuster bolts before using the tool..

1. Label all of the leads to the alternator so that you can install them correctly and disconnect the leads from the alternator.
2. Remove the alternator from the vehicle.
3. To install, reverse the above procedure. Observe the following torques:
   
   Pivot bolt: 58 ft. lbs. (78 Nm) Adjusting bolt: 25 ft. lbs. (34 Nm) Wire terminal nuts: 60-90 inch lbs. (6.8-10.1 Nm)
   

It could be the alternator. There are also a host of other things that could be the cause(s). Check the charging system to determine whether the alternator is possibly bad. A quick check is to measure battery voltage with ignition off, then again with engine running. Voltage should increase 1 - 2 volts with engine running. If voltage does not increases, then you certainly have a charging system problem.

Unfortunately the Honda alternator is regulated by the ECU, which allows the ECU to intelligently reduce alternator engine loading to improve fuel consumption. The intelligent system uses an electrical load detector (ELD) located near the battery to control the alternator output voltage. A two wire alternator has an inbuilt regulator that will always generate the required charging voltage. When a battery is fully charged and the electrical loading is low there is no need for generating the charging voltage, in this situation the honda alternator will reduce the output voltage to reduce engine loading, hence improved fuel economy.

you will have to check the voltage whith the engine running .should be 13.6 or better