I'd check the positive cable and the complete cable going to the back of the alternator also. Could be an issue there also.

 

I was driving the other day and my 98 f150 4.2s gauges all dropped to 0 and radio quit playing then stalled out I had someone jump me off and it died out again. So I brought my battery to the auto place and said it was good so I had the alternator checked and it was bad. Well I bought one from autozone and it worked good for a day then the same thing happened so a new alternator n good battery and even cleaned the terminals I have no idea what is causing this how likely is it this mega fuse and how do I remove/Replace it I hope thats whats causing my problem thanks in advance

 

Got the same problem as you. All fuses good. New alt. Gonna break down the fuse box and clean and reinstall this weekend. Also take alt back to autozone to be checked. Got battery voltage at alt but no charge. On way home tonight got misfire on cylinder 8 then when checking for provlem found plug wire loose. Reattached and when started all was good. Kocked the throttle up to check acc up on WOT. Then the batt light came on. Stick here at ground zero. Lemon in hand.

 

ford has had a problem with the little wire that plugs into the alternator. if you have this wire, the connection maybe the problem. Sometimes the wire breaks (inside) just at the connector. may help???

 

DID YOU FIND YOUR PROBLEM? I AM HAVING THE SAME PROBLEM, ANY SUGGESTIONS? i AM STUCK, REPLACED MY STARTER, ALTENATOR, BATTERY AND SOME MIMI FUSES. PLEASE ADVISE. THANK YOU IN ADVANCE FOR ANY HELP.

 

I had same problem I found right away.14 volts from the alternator is charging check it directly from the alternator,battery was good had 12 volts with no load on it..For my 2001 f150 super crew xlt it had a fusible link from dealer in the cable itself.You can perform a continuity test before opening up the loom to check the fuse.

 

check continuity from the hot wire on the alt to the battery where it comes up near the battery. Im thinking if it is rubbing on body ground it would short.. causing fuses to pop and the op's concern.

 

Thankyou but I was trying to demonstrate one way to diagnose the alternator and verify how to test the cables as well.True in fact a lot of people do have blown fuse in between the cable.For mine low voltage was the factor from the alternator.

 

Hey, I've read all the threads with the charging issues, and no one wrote what ended up being the problem. I was just interested in the conclusions because I am having charging problems.
I initially had a flickering battery light on my dash go off, and thought it was the alternator, but it was only 4 years old, with a 4 year old battery. I pulled the alternator, looked at the brushes, and looked worn, but not worn out.
Had the alternator checked, and said it was fine. I ended up buying a new pigtail harness, which I would return if everything was working fine.
I put the alternator back in, and the light went out, but going to work today, the alternator is not giving a full charge because the wipers were slow, and turning on the ac caused the voltage to drop.
I am wondering if it's the harness because I did check the fuses, and connections, don't know what else it could be?

 

The bigger problem in this thread is not knowing how the charge system works and just replacing parts and wondering around.
101 on the charge system.
A. The alternator has to turn a min RPM to output a voltage.
B. It needs a small supply voltage from the battery to generate a magnetic field with which to generate the voltage.
C. It needs a regulator to control output vs battery charge level.
.
How does the system work?
1. The regulator has a 'reference' to compare the Alternator output to the battery voltage.
2. If the battery voltage is lower, the regulator allows the Alternator to force charge current into the battery until the battery voltage rises to the reference level.
3. The difference between the Battery voltage and the Alternator Regulator value is what forces current into the battery to bring it's voltage up to the reference.
As this takes place the Battery voltage rises and the current reduces to a floating value.
.
Charge Lamp;
A. It is supplied battery voltage through the ignition switch.
B. The lamp is connected to the regulator.
When the alternator is outputting, the regulator 'removes' ground from the lamp circuit and it goes out indicating that the alternator is outputting.
.
Trouble shooting:
1. The battery has to be good.
2. The terminal connections clean and tight.
3. Field fuse good.
4. Mega fuse good.
5. Plug and charge lead connections all solid.
6. Alternator good.
.
Use a volt/ohm meter to make tests for fuses and voltage checks at the battery.
With a good system, the battery voltage will rise after starting to replace the charge taken out for starting. If it does not, the system has an issue and the charge lamp should be on.
Charge lamp flicker...worn brushes, intermittent plugup wire wiring.
Battery goes dead after setting some amount of time. Rectifier in alternator has shorted or some circuit in the truck is draining.
Lights change brightness. Often the regulator is faulty.
Dash gages swing full at cranking. Battery faulty or terminal connections need attention.
Other than more small detail this is all there is to the charge system.
When the battery voltage is not being controlled, what can be the cause from above.
Find the cause and not just replace parts with guessing and hoping.
If your confused about the circuits, look in a Haynes Manual page 12-17.
The charge and start circuits are all there in easy schematic form to see as described above.
Good luck.

 

Bluegrass very good info, as always. I vote that the mods put this in either the DIY or as a sticky in the elec forum, or both!