No charge

[DanHill]

Frustrated!
1975 F259 390. Does anyone know where I can find an electrical flow chart through the voltage regulator? I have a 105 amp alternator, which I believe is a 4 wire...? I have everything hooked up accordingly from the voltage regulator. A-armature F-field A- input of battery isolator and I to ignition to give me 12 volts to vr in the run position. No charge.
I understand for full field test that I can apply 12 volts to field wire to alt...?? Nothing happens. If I put 12 volts to stator, I get full field voltage. I have replaced the vr 3 or 4 times because I was suspect of it being faulty or the smoke rolling out of it told me to replace it.
I thought a flow chart might make sense to me. I dont mind being wrong but this charging system has worked beautifully for me tha last couple years. Someone please straighten me out on this. Also, I have been running dual batterys and a battery isolator with no problem for a couple years with no problems. I have tested the alternator at the local Napa, twice and checks good. Battery isolator also checks out. Does the alternator get excited from the field or armature?? Thank you for any help!
Small Engine
Bigfork, Montana

[cep62]

maybe this can help from the tech articles on the home page.

http://www.fordification.com/tech/schematics_h.htm

[DanHill]

Thank you. What I really need to know is about the Vr, 12 volts to vr at the "I" terminal, I believe. 12 volts coming out of vr is at the F or A terminal? Does the alternator get excited at the field or the armature?

[zgerbic]

Some of this will seem simple but you need to be sure they are connected this way.
If it is four wires to the alternator then one must be ground. There should be a ground at the alternator, connected to the regulator ground, and probably the body of the truck. Poor grounding can make the alternator put out low power levels, which is why Ford has a dedicated wire between the regulator and the alternator. The other three would be the Field (F), Stator (S) and the Battery (B or A+). These go one to one between the alternator and the regulator. The A+/Battery terminal on the alternator goes to the starter solenoid/battery connection.

A wire will come from the I terminal on the regulator to the alternator light in the dash. The alternator light will go to a switched ignition connection. This is one of the most important wires to check. You can spin the alternator and nothing will happen unless you provide a voltage on the I terminal through the alternator light. Power gets to the light when the ignition comes on, passes through the alternator light and then energizes the regulator. This allows the regulator to pass power to the alternator field winding, which provides the magnetic field that gets magnetically coupled to the three spinning stator windings, which makes three phase AC, which is rectified by the diodes to make 12V DC. The stator wire is used to provide a common negative/ground connection for the 12VDC power, though it is not directly connected to ground.

While the engine/ignition is off.
---Make sure the grounds are all present and the three wires going to the regulator are wired correctly. With the terminals pointing down on the regulator I think the connections are I, A+, S and F on Ford regulators.
---Make sure there is a good connection between the B/A+ connection on the alternator to the battery/solenoid. There should be +12 on the alternator A+/Battery connection.

Turn on the key to ignition position.
---There should be an 8V to 12V reading on the I terminal and the alternator light should be lit. If there is not, then you have a wiring problem or the light is burned out. A test to perform is to unplug the regulator terminal plug and short the plug I terminal to ground and check that the dash light is lighting up. Reconnect it.
---The F (field) connection on the alternator should also have about 12V on it, since the field should be energized now awaiting the alternator to start spinning.
---Start the engine and the alternator light should go out, if the battery is pretty well charged. If the battery is a bit low the alternator light should flicker but eventually go out when the battery is near charged.

If the engine is on and no power is coming from the alternator you can do the regulator bypass test. Safest to do with the engine off. Remove the plug from the bottom of the regulator and insert a jumper between the F and A+ terminals in the plug. I would use a piece of insulated 14G wire with the ends stripped back about 1/2 inch. Make sure you get the right terminals. I think F is on the end and would have a black/white wire. It may also be labeled on the regulator housing. A+ will be a heavy wire between the three other connections of the plug. Essentially you are jumping the battery power directly to the field windings of the alternator.
Immediately start the engine and see if the alternator starts providing power. A voltmeter should be reading 13V or higher on the battery.
If not, the alternator is probably damaged or miswired.
If it now provides power, the regulator is probably damaged, miswired or not getting power to the I terminal as described above.
Don't leave the jumper in for long as it will drain the battery.

Give this a whirl and let us know what happened.

[zgerbic]

Here are some pictures that might help. When troubleshooting a later vehicle, it is sometimes better to look at older diagrams which have less wiring, usually no alternate wirings and may have good color codes to go by.

1972 alternator wiring 3 wire plus ground.jpg

3 wire alternator plus ground.jpg

GENERATOR.jpg

[smengine]

Thank you very much for your help! I didnt have the alternator grounded to the vr. I thought I was grounded good but not good enough!