2001 F250 5.4 V8 4x4.

I have had my alternator tested and it was OK.
Bought a New battery costing me 100.00.
Even tried a new alternator and the battery light still stays on.

I read about the Mega Fuse and for the life of me I can not find it.
Passenger side firewall I see nothing.
I searched the whole engine bay nothing.
Looked in the covers can't find anything that looks like it.
Help me pics needed.

 

should be inline with the alternator or along the fire wall

 

I looked there and see one line marked FUSE but there is no mega fuse on it. Goes from the Alternator then branches to two grey wires connecting to the starter relay.

 

Do alternator diagnostics, voltage tests.

Come back with results.

 

The one marked fuse is the Mega if memory serves me correctly

 

I tried 3 new alternators and have had mine tested at autozone and it checks out fine.
The mega fuse came in today hopefully I can find where it goes otherwise I have no clue why the light flickers and doesn't charge and stays on sometimes too.

 

Bad ground?

 

You may have a fusible link. Sometimes two fusible links from the alternator's main charge/battery cable. May be gray in color labeled with 12 or 10 gauge. The two gray wires you mentioned going to the starter relay.


JJH

 

cleaned the ground and fuseable link tested fine at autozone.
guess i have to send it in

 

Use a Volt meter to check your voltage, when the truck is running voltage will be close to 14+ volts. If you get 14+ at the battery the alt is good. The wire going to the battery light may have a short or broken. One of the smaller wires from the alt goes to the battery light.

 

This may be an dump question but have you checked your battery light on the dash to see if its burned out or checked the 10 mini fuse under the dash?

 

Just thought I would let everyone know what happened so if they have these problems.
I brought it to a FORD shop and even thou I told them I tried 4 different Alternators and had mine tested they insisted it was the aftermarket alternators not outputting enough for my full power truck.
So I wait and they had to order a FORD alternator. It finally comes in and guess what? It wasn't the Alternator. So They take the inline FUSE out even thou it tested good at autozone and ford themselves from what I seen only some of the wire's inside where broken. Maybe not getting enough juice because of that? But of course when All is said in done they still insisted I needed a new Alternator so the final bill was $430.00!
What is the proper way a checking an inline FUSE if you don't have test gear? Hell the test gear didn't even help this time around it was saying the FUSE was fine.
So when it was said in done - Alternator and inline Fuse.

 

The only sure way to check a fusible link (and many kinds of fuses), is to replace it.

Period.

Much simpler than rigging up a tester.


Oh.. I would concur with them re Ford alternator.

 

kinna sounds like you got taking by dealer, but what else ya gonna do! makes me wonder if the inline fuse was just bad connection or maybe it was loose enough inside that it wouldnt work but showed good at auto part store. I am trying to find a solution to mine right now. see if you can help

 

I had an alternator go out on my '07 6.0L, and the slightly higher amp replacement I got from O'Reilly would result in a flickering battery light and eventually battery problems. Turns out the alternator wasn't making the proper power, some manufacturing defect, so they swapped it out for another one. That one was solid, and I never had any problems with it again, though I traded it in and who knows now.

Your case was a little more difficult to nail down, as it turns out, but it's not true that aftermarket alternators can't produce enough power. If you get the wrong model, then yeah, that can be a problem. Or if the alternator is defective, then that is what it is. In my case, the alternator was capable of making MORE power than the factory one.