6.4 Coolant temp barely above C after 25 miles

[AmarilloF250]

Just trying to figure out what might be the issue. Started my truck this morning about 10 minutes before leaving for work. Came back outside and the coolant temp was still below the C which I didnt think much of it at the time. After driving 23 miles to work the temp barely made it above the C on my guage and once i parked i let it idle to see what it would do. It then proceeded to drop back down below the C after idling for 5 minutes. It was 39 degrees this morning and i have no mods

 

[AmarilloF250]

Im gonna try changing the thermostat but any other ideas

 

[Gunnin]

I'm guessing like you it's a thermostat stuck open. I've had this happen on a gas vehicle and a bad thermostat was the issue.

 

[Scooter's Roofing]

there are two thermostats on that truck. Not a fun job IMO