2003 Ford Excursion 6.8 4x4280,000 MI Haven't had this truck long. Had a quirk in the temp gauge when I got It:

Sporadic temp gauge wavering and dropping down to resting spot then dead then would come back to life. Would throw a 1289 code pretty often.(Head Temperature sensor)
Towards the end laid low almost in the dead position but wouldn't throw a code and AC works

Now just lays there dead. Check gauges light not check engine light comes on immediately. Once I run it the 1289 codes comes back
This disables my air conditioning.

**** just got real. I'm 57 overweight and high is supposed to be 90 today. Nothing like driving a black greenhouse around in this weather with no AC.

Here is what I have done so far:

Guage passes sweep test.
Replaced Head temp sensor no changehave 5 volts at harness
According to ford diagnosis yellow/red should be under 5 ohms resistance. It shows open circuit.

Flow chart says repair circuit.
Is there a place to Chase the harness for a notorious wear spot or breakage spot? I'm assuming that's what they want me to do is look for a bad wire?

What Am I chasing here guys?

 

This was the culprit. Cut both connectors off and spliced together TADAAAAA I HAVE AIR AND A DUMMY NEEDLE BACK!

 

Crazy THING I am in three Excursion groups,
two Ford groups
and nobody answered me....usually by the time I post something there are people chiming in.



Guess I had to do this one myself...
Amazing what you can get done with razor knife and a meter😎

IDOMYYYYSELFFFFFF

I HAVE AIR AND A DUMMY NEEDLE BACK!
Hope this helps someone in the future. DON'T OVER THINK IT!

 

Persistence pays off. Great that you found the problem and shared your findings. Congratulations !!!

 

Nice work.

In 20 years or Ex’s i have yet to encounter a issue the factory service manuals and the pinpoint test don’t lead to the resolution.