Webmaster's Notes: When
creating the colorized wiring diagrams for the
1966 model years, I compared the two to note any
differences between them. I decided to scan them both and
then (using Photoshop) layering them over the top of each
other for comparison purposes. I found that the two diagrams
are absolutely identical. They literally used the 1965
diagram to make the '66 version. All circuits are numbered
and colored the same and have the exact same path...with one
CLICK TO ENLARGE
The main harness circuits going
into the connector at the base of the steering column for
the turn signal switch are identical...but the two diagrams
seem to show a different destination for the circuits up
inside the turn signal switch itself, after the connector.
So this made me wonder if this
is another Ford engineering SNAFU that got past the
proofreader or what, so I started doing some digging in the
MPC to see if there was a different switch used between the
'65 and '66 models. Here's what I found:
(less mounting plate)
61-62 F100/250 2WD
61-66 F350, 61-65 F100/250 4WD, 66 F250 4WD
63-64 F100/250 2WD
65 F100/250 2WD, 66 F100 2WD/4WD, 66 F250 2WD, 67-69
F100/350 "Before Ser. G30,001"
can see, there were actually four different part numbers
used for turn signal switches used in the Slicks era. In a
nutshell, the '61-'62 2WDs used one, all F350 and 4WD
up through '66 used another, '61-'64 2WDs used a third one,
and the fourth was used on '65-'66 2WDs and '66 4WDs.
So...considering how the original diagrams themselves are
("F100, F250 6 & 8 Cyl.") and don't show actual application,
to me that means essentially that the wiring harnesses
themselves between the '65 and '66 trucks are identical, and
although the turn signal switches might differ slightly in
application, they still connect to the main harness using
the same connectors and circuits.
I'm still researching this and will update as more
information becomes available.