F-150 fan clutch issue: second act

Let ne take off the PC verbiage...

With *ANY* data logger plugged into the on-board computer systems...without
adding new sense points...will just beget you whatever the computer
systems will tell...which is already been gone over numerous times
by the dealer (big assumption)

I'd have asked them to put thermal couples on many, many more points
AND employed an IR thermal gun with sheets for each measured point
that has several lines for several shots of each point

Won't tell exactly where the root cause is, but a better picture of
where it is...

First...repeat...the computer systems is being told that the fan clutch
needs to be turned on

Why is the biggie and the forensics thereof

Also, a divide and conquer methodology is best here....plus the fact
that it did so for years at the limits to maybe over the limits might
have taken it's toll...

It is it in the bypass...easy with an IR Gun and/or data logger reading
thermal couples on both sides of the by-pass valve and the associated
components involved that that function

Several data points both thermal couple and IR gun around the main
radiator...including several points on both hot and cold tanks...and
the engine oil & ATF lines (both in and out)

Then the thermal couples on the engine and tranny...many, many points
but understand internal points most likely can not be accessed and
where the on-board computer sensors the only things available

ON that...any scan gauge will just read the on-board computer sensors
and no more...unless you have added 'new' points to be measure with
new thermal couples

Bottom line is to paint/gather a complete thermal picture of the
*WHOLE SYSTEM* and with multiple logged events. From the base line
first thing after an over nite cool down. Then a few minutes after
turned on, but still in the drive way.

Then drive around the local area (all with the trailer hooked up)
and then some freeway to establish other datums

Then go out on the freeway as if going RV'ing and the terrain & driving
style. Of course fully loaded

Key is to get those datum points BEFORE the issue occurs....then log
many, many data points during that event.

Here is the one aspect many miss in doing this type of forensics...keep
the data logger hooked up and KEEP logging points during the cool
down phase until the fan clutch turns off by itself

Going with just the on-board computer systems and their sensor points
will have you and them going in circles with the same data each time...it
turns on the fan clutch because the on-board computer systems has
told it to...