Lack of heat

[frost]

2016 Ram 2500, 6.7L. Problem - very little heat! OAT 18 degrees, heater temp set to highest heat setting but very little hot air came out its just warm at best.
Prior to above issue my Truck had been to dealership for unrelated issue. I requested they check the engine fluids, apparently after checking (maybe added?) to expansion tank level the so called technician neglected to check the tank cap which wasn't tightened & allowed anti-freeze to spew out.
I had to add ant-freeze to bring it back to proper level. Now the no heat issue, I am thinking there's air in the heater core? What is a normal operating temp? My temp shows 192 - 197 degrees. Any help/ideas appreciated
Glad I'm in AZ for winter not back in CO!

 

[TMyers]

My truck runs right at 192 degrees. I just drained my entire cooling system over the weekend and 4 gallons filled it to the correct level at first. I drove the truck about 10 miles, and it held another half-gallon. Today, I drove about an hour and checked it, and it held another half-gallon. Something I learned this weekend that I did not know... The half-inch pipe fitting that threads into the head that feeds the heater core is a flow restrictor. Both heater core lines are 5/8" along with the hoses but that fitting is restricted down to about 3/16". I'm guessing that is to decrease pressure from rupturing the heater core.