Good morning,
I have an 05 F 350 PSD. Yesterday after I started up an pulled out into the 5 degree morning, the speedometer went up to 70 MPH and stayed there even at a full stop. As I start moving, it moves up to past 100 MPH and then back to 70 as I slow down to a stop. This is just normal driving 35-45 MPH. Any ideas?
Mike

 

Cold outside and so is your trucks speed sensor.

 

OK John, the truck is garaged at night, 45 degrees. the speedo sits at 70 even when the truck is off!
Mike

 

You could try holding down the trip button on the dash when you turn the key on and see off the gauge sweep will get it to come back. It's how you enter the engineering mode. There is also a digital speedometer in there when you scroll through the options.

 

I would look and check the VSS sensor connection on the rear for corrosion.

 

If you have some type of digital gauge like the SGII or a smartphone
app. Look and see what it is telling you for MPH. I have a feeling that
the cluster is where you are going to find the problem. Getting the cluster
to go into the diagnostics mode would help.

You can send this user a PM and ask for some ideas. Ford Truck Enthusiasts Forums - View Profile: CircuitBoardMedics

They work on these and also there is Ed over at http://www.ficmrepair.com

The cluster uses little servo motors to move the pointers.
One other thing I have heard about happening was the tiny
white spiders will get in and build a nest and the web strands
can block the needle movement,


Sean

 

I have the same thing that happens on my Mustang, it is the stepper motor that's bad on it, in 2005 there were a bad batch if them.

 

Actually it is not usually a bad stepper motor but rather the needle gets hung up slightly on the gauge face. Mine did that a few times one winter and hasn't been an issue since. Usually happens when it is cold. There is a tsb on the issue.

Sent from my Telegraph using IB AutoGroup

 

See FORD---TSB 07-11-2. See link.
.
https://www.ford-trucks.com/tsb/fulltext/show_article.php?tsb=07-11-2
.

 

We gave the original posters a wide variety of ideas, guess we need him back in here ...