The cooling system can be stopped up and the heater control valve could be closed for some reason. The climate control system could have an air door problem. Sounds like youv'e done some cooling system service. Did the system work OK before you got it worked on? If it did the repair work may be the cause then on the other hand if the repair work was done to fix the heat then maybe the car wasn't checked for the cause of the probl;em correctly. Sure the therostate and the coolant needs to be right and the system has to be truly full and this car is difficult to get filled right. A good test is with the car warmed up, the upper coolant hose should be hot to the touch maybe too hot to touch the heater hoses should also be hot, nearly as hot as the upper hose. The upper hose can be cooler than the heater hose if the car isn't fully warmed. I f the heater hoses (theirs two) aren't both hot then the flow though them needs checked. If none of the hoses get hot then theirs a basic cooling system problem. The tenperture gauge should be in the middle or 190 to 215 F A meat thermoter can tell right at the hose to the therostat housing. If not it's not full the stats bad the states not the right one or installed wrong. Lets say it's right. remove the hose from the easiest place with a drain pan under it garden hose blast the connection that goes to the heater the coolant should blast out the other connection. Just enought to see it do it. Connectit back up and try the car again. Cars that are put together with inproperly mixed antifreeze can clog with pure antifreeze as it'll gel up at high and low temps. It has to have the right mix to work right. Too miuch in the mix is as bad as not enough. The flow is good and the hoses get hot the next is the air doors in the heater box. Or did a mouse build a nest in there and they didn't like the hot air and packed it full of stuff. The critter may not be there now but his nest may stil be there or nuts he was storing there. Even though the air is coming though the door may have rusted shut as it was closed all summer and the AC condensation rusted the door and its stuck

It is located in your dash in usually the passengers side and in a hard spot to get at. you should see 2 hoses head into towards your dash when its cold take em off and blow air or water through them to see if it is plugged first and you may be able run water to blow the junk out if your lucky.