dcoll1957

I have no control of water through core when I move the temp dial to hot sometimes I get heat

Sometimes I don't what does that dial control a door or some type valve 2003 dodge allstock

FMB

Nobody has control of the water flow through the core unless they modified their truck's system. That dial controls a door that diverts more air flow through the heater core for more heat, or less flow for less heat. If you are getting back and forth heat and no heat conditions, without moving the dial, you may have an air bubble in your coolant system.

There are lots of issues with the doors on the HVAC system. Search the site or go to Heatertreater and see their solution.

Jeff in TD

There are a pair of blend doors that direct air through or around the heater core. They are controlled by stepper motors, who's travel is supposed to be limited by tabs on the hvac housing that interact with tabs on the couplers that are between the motors and the blend doors. These tabs can break, leading to the breaking of the blend doors.

The AC must be evacuated and coolant drained, and the entire dash is removed as a unit in order to get the hvac case out to replace the doors. I think there was also an updated version of the upper and lower hvac housing.

Aftermarket wise, there is a company that makes metal doors and they have a system of cutting access into the hvac case without taking it out of the truck. Heater treater I think it was.

Anyway, this thread shows the hvac case well, and links to the procedure for removal.

https://www.dieseltruckresource.com/...rstood-210483/

Hope this helps. I had the hvac case out of my truck. Not complicated, but it takes about 5 hours to remove.