No Heat

I would check out your heater core. Could be damaged, clogged.

I had the heater core flushed by a shop and it seems to be ok

Your truck has a heater control valve that diverts water to the heater core. That valve could be faulty.

try changing your temp control sencer,is on the engine,should be next to the thermostat housing screwed into the intake,one wire going to it.if your truck has a manual gaudge their will be 2 that look alike unplug one to see if the temp gudage dont work,you need the one that goes to computer,tell this to the parts store.

does it only work on cold ? it could be the blower motor reistor but they are right it is probably the heater core

These trucks seem to have an issue with the blend air door in the heater box. Good heater core, hot coolant, and still very lukewarm heat. Somehow the cold air is still blending with the hot, this seems to affect AC, too, as it isn't very cold. I'd like to find an easy way to fix the blend air door or block the cold air in winter without resorting to duct taping the cowl vents, or spending a couple grand on pulling the heater box in a 20 year old truck.

No need to look at all that other stuff. It is a design flaw in 6 cylinder Dodge Dakotas, Watch this Video, Its an easy fix. https://www.youtube.com/watch?v=7Sjqvai14ts&t=318s

so which one worked

Is my 1994 Dodge Dakota 3.9 liter V6 Magnum motor supposed to have a heater control valve do they come out with the heater control valve