HELP??? temperature valve

what does the temperature control valve look like??? is it atached to what looks to be a heat sink????? i have no heat, heater core is flushed, new ranko valve, new thermostat, car runs at mid on the temp gauge, just will not blow hot air, heater core looks to be in excellent shape. car is a 92 roadmaster with the 5.7 in it. any help would be greatly appreciated and very much needed, thanks in advance