If we are all having issues with the heat in the 5.9's there has to be something else doing it. My guess and as someone mentioned to me in another thread is its sensor related. Maybe the temp sensors in the dash arent what they used to be or something ?
See i dont have an issue with heat, my heat can get so hot itll burn me. My problem is the heat comes and goes, its wierd.
I wouldnt put a 210f thermostat in there if i were you. These engines dont like running hot, why dont you just unplugg the low speed fan sensor and leave the high speed plugged in ? That will raise the vehicle temp up to what a 210f thermostat would.
Candyman; mine does the same thing but I have to be sitting for a decent amount of time to make it happen, while driving its never above what the picture above shows, has to be sitting idle for a long time to actually hit 210.
As far as the 195 vs 205 I thought of that but a few people on the RAM forums have run the 205 degree thermo's in their 5.9's without issue and actually increased their gas mileage in the process, only by a few 10th's of an mpg, but I think I'm gonna try that first.
I did do a little testing with the thermo I took out, which was a standard Stant 195, against the Stant SuperStat 180 I had bought and noticed something slightly odd.... at the point the cheapo 195 stant was fully open, roughly 185 degrees water temp, the expensive SuperStat 180 was only half way open. Part of the issue may just be cheap POS thermostats. I have a 195 SuperStat on order but it wont be here till monday, after I swap in the SuperStat I'll post up my results.
As far as the fan switch goes, I also found 220 degree fan switches which may let the engine heat up to its optimal heat range before activating the fan. Either swap will be ok since 10degrees is far from causing a catastrophic failure and may fix, what seems to be, a 5.9 issue for those of us living in colder regions of the country.