My heater is not working?

Thanks fixitmr.I'll see if I can check it tonight and let you know.

Well, I checked the blend door & it works fine, I can hear the thump. Come to find out that someone had replaced the heater control valve a while back (it's my sister's van and she couldn't remember when she got it worked on), but there seems to be an extra vacuum hose that comes out of the firewall and plus into nowhere, so I'm assuming that the line that's messing up her heater operation. The other hose that comes from the firewall connects into the control valve and it you can see that it opens and closes the valve as you turn heater off & on. Now I have the task of location a diagram that shows where all the hoses are supposed to connect. One odd thing.I switched the hoses to go into control valve to see what would happen. When I connect the one I found loose into the control valve some heat does blow from defrost vents but doesn't operate the valve. Other than that still no air from other vents. Still searching.

Heater problem
1990 Dodge Caravan 6 cyl Two Wheel Drive Automatic

my heater was working fine one day then get in it the next day and it wont work. We changed the fuses and had the blower motor checked it isnt any of these, but the heater still will not work. What else could be the problem for the heater not to work? I have tried everything I could think of, what else could it be

I have a 1986 dodge caravan with a 2.6L mitsubishi engine. I changed the thermostat twice last week, bled the heater core, and the radiator is full. The engine runs cold and I have little or no heat. What is the problem, I'm out of ideas.

Even after running for some time (enough for engine to be up to temp), the temp gauge barely reads above cold and the heater puts out luke warm air at best. When I turn the heater off, the temp guage rises slightly.
With the engine cool I opened the radiator, but it would not take anymore fluid.
Is this a thermostat problem? If so, where is the thermostat on this vehicle (I've changed others in the past)?
Is it a heater core issue? If so, how do I flush it?
Or is it possibly just a coolant level issue? The fact that it won't take anymore concerns me. Or is that because I checked it while it was cool?

Any advice is appreciated. Thanks.

I drove it the other night for about 25 min's at highway speeds, the temp guage barely got above the cold mark, the heater put out only luke warm heat, but the engine didn't appear to be overheating. Does that help you narrow in on the problem? Thanks.