Dodge Repair: low heat output: 97 Dodge 1500 Pickup

Question
I have a 97 dodge 1500 extended cab pickup with a 318 engine. When I turn the heat all the way hot I get slightly warm air from the vents. When I turn it to defrost it gets cooler. I flushed the heater core and the coolant is full and a 50/50 mix. the thermostat is working fine. What is my next step? Thank youl

Answer
Hi Bill,
I suspect that the blend air door inside the HVAC unit may not be moving fully to the position where it diverts most/all the incoming air to the heater core. As stated in my 'expertise' paragraph I don't have manuals for trucks of the 90's but I would believe there is such a door in your truck. It may be controlled mechanically by a cable, or there may be an electronic actuator that is out of adjustment or the door is binding up. So take a look under the dash to see what moves on the box when you change the temp request.
If it is an electrical actuator, remove it (three screws) and then use a tool similar to the actuator's lever to see if the door seems to move freely or not. Mate the actuator to the door carefully when reassembling.
There might be an HVAC calibration procedure you could try. So describe the control panel and I will see whether it might be similar to one used in the cars of that vintage for which I do have the manuals.
One last possibility is that even though you flushed the core it may not be open fully. Touch the two hoses that pass through the firewall and note whether both are equally warm or not. If one is significantly cooler than the other then the flow is not sufficient.
Please read the PS below and respond to it.
Thanks,
Roland