I went to change the temp sending unit on my 98 3500. And when I look at the back of the head on the left side all that's there is a plug. Did they move it on a 98? I can't seem to find any info on this but I am still searching. Thanks William

 

The only sensor I can find that screws into the water jacket. Is right between the filter housing and the injection pump at the bottom of the head. It looks like it has 4 wires going to it. I always thought that was for the fuel preheater (Long gone) And the preheat grid. Does this sound like the temp sensor for the gauge? Maybe they were combined in 98 to get ready for the 24v. Anyway the sensor from dodge that i just got isn't going to work. So back to dodge in the morning

 

Sound like you found it, but it should only have 2 wires. Its the only sensor on the truck that has a pigtail extension on it.

If you can't get it from dodge, I got mine from Rockauto, its an AIRTEX / WELLS 5S1032. Because a 12 valve 98 is only a half a year it is sometimes difficult to get the correct parts for it.