My truck never did this untill I installed a new tstat from NAPA. Nothing was wrong with the old one but the seal was leakin so I figured as long as I had it apart I'd stick a new stat in it. Now I can watch the guage run up to 190 then drop down to about 140. Freaked me out at first but it dosn't go over 190 so I got used to it.

 

I have a 1996 Dodge ram 2500 and i have replaced the thermastat radiator and also had a system flush and i still have no heat can anyone help me out please

 

Theres a sensor on the back of the motor that controls your gauge sometimes they go bad or get loose and that will cause your temp gauge to act up.

 

I have a 97 & it does the same thing since it hit 68,000 mi. Now has 198,000+. Still drives me nuts & like others, I watch it all the time. I may try the updated t-stat

 

Mine only does it in the winter. If it's really cold, well below freezing, and I don't go off the highway, it will only do it once. Warm up to about 195 on the gauge, then the Tstat opens and it plunges to about 150 and stays there. If I'm doing mixed driving it's up and down like everyone else. If I let it idle too long in the winter it stops warming up and starts cooling off, eventually it cools off almost completely. My heat has never been good, it's only ever warm at best. New core, system is full. It's always been like this as far as I know, I've put over 200K on it, as far as I know the first 125K was no different. Just an old horse doin' what it's always done like these old horses did. I've heard rumors that they aren't all like this, but I've never had a mechanic under it who could find anything wrong

 

In the winter .. put some cardboard in front of your radiator .. . I have my CAC and all covered up ... right behind the grill and such .. my heat is awesome .. runs me out ..

 

My truck does the exact same thing during cold temps, and I have the new part# tstat. Sounds silly but I jack the front end of my truck up real high to hurl my system. It's always worked well for me. .