I replaced the alternator. It looks like the voltage regulator is inside the alternator, but a mechanic told me it's not. I can't find any external thing that I recognize as a voltage regulator. With the battery fully charged it has 12.6V at the battery terminals. With the engine running at 1,200 RPM it still gets 12.6V at the battery terminals. The battery light is on in the dash, and the amp meter in the dash only says 4 or 6. But running the engine (especially if I need to use headlights or wipers) drains the battery. The wires from the alternator to the battery check OK. Some other guy pointed to a metal box on the driver's wheel well and said that box might be bad. I have a picture of it except I don't know how to post images here. It's a box about 5" X 6" X 1" mounted on the driver's wheel well, just forward of the master cylinder. If someone can tell me how to post the picture I'll do that.

 

That "box" is not your regulator and would not affect charging. Im pretty sure you have an internal 2G alternator. Search 2G alternator and see if the pic is what you have. Most parts stores will check your alternator for free.

 

If it's an '87 you have a voltmeter, not an Ammeter.

You also have a 2G internally regulated alternator.
If you changed the alternator you should have changed the charging pigtail as well.
These are a known problem, and the main reason Ford went to a stud and eylet charging connection on the 3G (third generation) alternators.

These should be available at any auto parts store for under $15.

If you need it I can post the part #'s from six or seven manufacturers.

 

Yes, voltmeter. 4 to 6 is volts. So I'll replace the pigtail and see what happens. You have a NAPA part#? Or any place else we'd have here in Gettysburg, PA?

 

very common to have replacement alternators be bad out of the box. Id still have it tested when your at the store getting the new plugs. Those plugs are a readily available item.

 

NAPA Part: ECH VRA400

 

Another common problem least where road salt is used is the brushes wear down but more importantly the springs behind them rust/corrode leaving the brush or brushes with very little or no pressure pushing em against the armature. Brush guides get fowled with crap sometimes too, brush no longer able to move toward armature as they wear down. Once contact of one or both brushes is lost, that creates a no charge condition such as you have.

Voltage reg can be serviced with alternator in place on motor however if original factory engine hosting bracket is still in place on the 460, its a little tight to get to the 4 torx screws holding the VR in place. Get em out, put em back in, easier if remove alt.

Brushes and their springs are easy to inspect/replace. If you do pull it off the back of the Alt you'll need something hold brushes up in place when putting the VR back on the Alt. A common strip type feeler gauge works perfect, one thick enough have little back bone is all it takes.

NAPA AUTO PARTS

Naturally you can buy the whole voltage reg if needed rather then just the brushes and spring kit. However the bulk if it is plastic once those parts have been removed.

 

White-97-XLT, is that the pigtail for an '87 or a '97?

Danr1, the alternator is new (or reman), so I wouldn't suspect brushes or springs. Actually, when I checked the wires coming from alternator to battery I had to work the probe around inside the connector until I got it to register. Maybe it IS a problem with that connector/pigtail?

How would I check alternator output while it's still mounted to the engine? If a pigtail won't fix it I was thinking of charging the battery and starting the engine and then testing for amps coming out of the alternator. That way I wouldn't need to remove it from the engine and take it to be checked.

 

That plug is for the 87 (2G) , the 97 (3G) does not use the problematic plug!!

 

You can "full field" the alt by grounding the screw on the back of the vr marked "ground here to test". Have your meter on the battery and you should see high 14 volts

 

Nope and neither would I, sorry bout that totally read right over that part (first four words in opening post in fact ) where you stated alt was replaced.

Well if it helps someone else at some point guess it was worth mentioning anyway.

 

For anyone else searching this thread and needing the info, also;

Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman 85123
Motormite 08622
etc.....


Hey two4two,

You have that cool retractable rear window.
Is it functional?
Do you know how many Bigfoot models were made?

 

OK, I replaced the pigtail (yes, soldered and shrink wrap), still only 12V at the battery with engine running. That is to say the alternator is sending no juice to the battery. I'd like to try that suggestion about connecting the correct post from the alternator VR to ground and doing the full field test to see if high 14V is indicated at battery.

 

Here is a picture of the back of your voltage regulator, Note there will be screws in the two holes at the bottom. (Actually there will be screws in all 6 holes, but the only one you are concerned with is the bottom left, (inside the plastic)). Just put a ground to the left one (with the engine running of course) and it should make the alternator charge full.. If not the alternator has problems.. If you do get full charge there is something in the wiring on the truck not getting the power when it should..

 

Hey White 97 XLT, is that part you've sent actually on the alternator? I have a hard time seeing one like it on my alternator. But let me ask you, if I find ANY lable that says "F" or "FIELD", can I do the same as you suggest to ground it and test? I have some pics of what my alternator looks like. If I knew how to post them I would. Anyone can tell me how to post pics? I see in my priveleges it says I may not post attachments. Maybe to e-mail it to you?