67 F-100 Battery not staying charged new alternator not fixing it.

[BarneyGeo]

I have had problems with the truck since I have dropped the newest engine in it. I found a short in the headlight switch. I changed it out. I then had the alternator checked and it was putting out about 12. The store told me it should be around 14 so I changed it out this last week. I have driven it on a daily basis short 40 -50 mile trips and it would not start today. When I left the house it turned with good fire. When I got to my stop it would not turn over more than twice. I had to jump it off.

When I put the alternator on the truck when I was rebuilding could I have a wire or wires backwards??(Could this allow it to do its job while running but still not charge the battery?) It acts as if the alternator is not charging the battery back but is doing fine while running with all other electrical items.

Thanks for any and all help. This forums is amazing. I could not have gotten my truck back on the road if it had not been for this group!!!!

Thanks again,

Joe

[unclebubbles]

Unless someone has changed it, the alt. on this truck uses an external regulator. It is usually mounted on the pass. side fenderwell, or somtimes next to the radiator on the cowling. The original was probably a mechanical unit, but solid state replacements are available. Auto zone, or most parts stores can check them for you. First make sure your batt. cables and ends are in good shape, and clean. Check your grounds. Run a ground strap from the motor to body, batt. to body, and ground the frame, make sure the metal is clean where theyre mounted. Also, the regulator needs to be grounded, and the alt has a ground terminal, make sure its grounded. Test the battery, make sure its ok. Try this and post back if you still have problems. On old vehicles like this , its usually a ground problem, or the regulator. Good luck.
Later
Ed

[BarneyGeo]

Hi,

I have checked all of the grounds and done as you suggested. The only "thing" I am unsure of is the alternator ground itself. I had a black wire that was in with the other wires to the alternator that had a huge ring on it. I assumed it went to the engine where the battery ground is located. I did not see other wires that I thought were ground. Is there a standard "wiring diagram for the alternator itself? I think I have hot on its terminal and everything else on one of the other terminals. I have two connection bolts that have nothing on them?? Is this correct? Any and all help is appreciated!

[unclebubbles]

working with something this old, you never know if someones cut wires, added wires and changed the colors, or if its even wired correctly. The original alt. would have 3 insulated terminals marked: Batt Fld Sta . The regulator is marked the same, with an additional term. marked I, this is for the indicator light if it has one. It would have a couple of bare studs , one marked Grd. Assuming youve had the alt. , reg. , and batt checked and theyre all ok, disconnect the wires from the alt. , and the reg. Disconnect the batt. Check for continuity between the alt wires, and the reg connector. Color codes arent always what a book says, but the Fld should be orange or brown. The Sta should be w/b or g/r . The reg term marked A. is batt + , and should go to the starter relay, or other 12v source, check it for power. There shouldnt be 2 wires on any of the alt terms, except maybe the grd. Also , check for current draw with the key off. Something could be draining the batt. A bad diode in the alt, or a bad reg can cause the field to stay energized, and drain the batt. Email me, and ill send you some diagrams. Good luck.
Later
Ed

[BarneyGeo]

Thanks for writing, I bought a new regulator, changed wiring on back of alternator BUT there was no wire (green) for the FLD. So there is no wire on the FLD post. I had Advance check and I had NO juice coming into the battery BUT the alternator, after changing wires to correct post was putting out. Where does the wire come from that goes to the flow? Maybe I can track it down if I knew where to look.

I had a guy suggest the starter relay?? I still want to know about this 3rd post with nothing on it!

[unclebubbles]

Reread my post on the color codes, and source voltage. Some vehicles with an ammeter instead of the indicator light, didnt use the stator term on the back of the alt, or if they did, it was for the choke heater. If this is your case, you may have the fld wire on the sta term. Im gonna send you some diagrams that should clear things up for you. Since i cant see what you have there, im shooting in the dark. lol Check your email.
Later
Ed

[BarneyGeo]

Found wires were reversed on alt.! Charging at about 14 now!

Thanks for all the help!