No heat sitting still

my 89 towncar, not driven very often, but i have been driving it lately, and ive noticed that while im driving the heat will run you out, but when i stop at a light, the air blows cool. Does this sound like a thermostat? any thermostat problems ive had have been the opposite

might have a small vac problem, when running your engine produces more vac (enough to keep the blend door closed) and when you stop it drops. (this could be backwards but this may be the problem. Or if you have a really low idle you may not be moving enough fluid through your heater core. pull the vac line to your blend door (behind the glove box on the left) and see if that helps any

would that line also control the door which changes from floor to panel? when on ac after running a while, all doors will close and the fan runs, but nothing blows out. do i get to this from the inside or the outside?

all of your AC/Heat doors should be vac controled. All of the vac lines run in the dash, I could post a vac diagram if you need one, could also be a bad heat/ac control panel. Figuring out the climate control is a PITA and often best left up to someone else.