If all of speakers are crackling, it is probably an Amp issue.  If it is
only one speaker - the wiring from the speaker through the door jamb to the
interior probably has a bad spot from the opening of the door.

To Captian Coleman alone:
If the reasoning behind your post was allowing for the speakers
"crackling" due to the Ford amp being overdriven (clipping the input),
then you were certainly on the right track, and the following wouldn't
apply.   ;)

I'm posting this from the standpoint that he has an amplifier with
problems (or damage) -and to me, if that's the case, the POS isnt
worth repairing (or even using in the first place if you have an
aftermarket head unit of any decenct account) lol

Nice idea but...not "entirely" accurate. (no offense)

I have the same truck (94 XLT), and there would be nothing for any
replacement harness to plug *into* at least per your quote:

The only "factory adaptors that I've seen at Crutchfield and the like,
do NOT bypass the amp (without running wires). They simply adapt
speaker-level output from your aftermarket stereo, to the oddball
fixed-input level design that Ford decided to lock everyone into.

That is, the signal that Ford's built in amp requires is neither
speaker level, nor RCA-level. It's somwhere in between. ;)

There's only two ways to *truly* "bypass" the factory amp.
One requires running 4 separate pairs of wires. One from each door
speaker to the area that the head unit rests in. OR the the way that I
ended up doing things. (which was a time/frustration saver, as opposed
to running things 100% dash to speaker)

I didn't fancy the idea of having to go through each individual door
jam assembly. So, while I was considering the task of running 4
separate lines to each door (and then obviously to where the head unit
rests)...I stumbled across a "central harness" point that allows you
to tap into all 4 speakers at one convenient junction.

Bottom line: I still had to run 4 pairs of wires, but averted having
to go into each individual door!!! (I simply ran the pairs from the
stereo in the dash to the area between the passenger side doors).

If you would like to do the same, there's a quick-connect point that's
at the base (under the floor/side panel molding) between the passenger
side doors (in the dividing frame, the same one that the rear pass.
door mounts to).

You have to remove the single piece of floor molding (that extends up
the sidewall) on the passenger side, but once you do, you should be
able to see a little opaque-white connection box, that feeds both the
amp, and the speakers. It'll have roughly 10-12 wires. (hint: it's not
within the wiring loom that feeds nearest the rear passenger door
rail.) I don't remember if I used the male or female side of that
connector, but one side comes FROM the amp,  and the other goes to the
speakers. At least Ford afforded us that much! A nice little tap
point!

Sorry that I didn't retain the wiring pinout that I created while
sorting out which wires went to which speakers (color codes and
polairty) once the job was finished... I even thought about it.
I just figured... no one here would want to go to the same trouble I
went to for the sake of "quality sound". (translation: for most, it'd
make more sense to just pay some stereo joint to have it installed.)
But if you have the basic knowledge of how to install a stereo
properly, it shouldn't be too hard to trace speaker wires... ;)

Something told me to save that little piece of paper...