Drove my truck today 25 miles in city/hwy at ambient temps around 45-50 degrees F. I have driven this amount tons of times and had normal operating temps of about 180-190. Today the needle barely got to 140. Is my thermostat stuck open and in need of replacement? Any reccomendations on models to buy that work well if this is the problem?

Any threads that show how to do this and not install it backwards which I hear is very easy to do? I have never replaced one before and not even sure where it is on the engine. Thanks for your help.

 

Best to use a stat from Cummins, p/n 3928499.
Instructions> http://dodgeram.info/tsb/1994/07-07-94.htm

 

Check the coolant level 1st.
If you need to change the thermostat, It's under the thermostat housing/water neck. (thing that the upper radiator hose clamps onto at the engine end of the hose).
Just remember which direction the old one was in. Put the new one in same direction.

 

If you have to change out the stat, there is a big difference between a OEM and a car parts knock off, do yourself a favor and go to Cummins QuickServe Online

When you register, you may view information specific to your Cummins Engine, including: Your Owners Manual, the Parts Catalog for Your Engine Serial Number, Engine Dataplate Information for Your Engine.