Toyota Repair: inside heating problem, heater control valve, control cables

Question
hi! i have a 4runner 1990 4x4 sr5. everything seem all ok to me except for the heating inside the truck. the truck's engine get hot very normally and at a normal speed for the weather we have in canada. but the air coming out the fan is always cold... i tryed changing the thermostat and nothing changed, i flushed the coolant, cleaned the collant system, chang cleaned again and then poored some new coolant. and yet nothing changes.... when im driving the truck, the air get abit hotter inside but if a stop on a red light the air get back to cold right a way... it doesnt keep up with the cold outside, so my windows are always frosted and it doesnt melt nothing... and my feet or frozen. it been doing so since i bought the truck 1-1/2 year ago.. i dont think its normal for a v6 to have such poor heating inside. let me know if you have a solution.

Answer
Check all the control cables from the dash, move the hot/cold control and make sure the control lever on the left side of the heater unit under the dash moves and is not disconnected, check on the right side to make sure the defrost door opens and closes when moving the air control slider through all the ranges, if there is no problem there the heater control valve under the hood may have become disconnected or has stopped working, the last possibility is that the heater core may be clogged.