Please help. Iam having a little trouble with heat.

[Dean Malaxos]

I just bought an 87' LX with the 4cc motor. I absolutley love this car. It is by far the best $400 I have ever spent. It runs well and is very clean, esspecially the interior. Anyway when I turn on me defroster it blows out hot air only. I thought that it may be the thermostat but I was told that it probably isn't as the car is not over heating, the thermostat is right where it should be. I was also told that it could probably be the heater coil valve. The guy said that it was in a radiator hose. I really know nothing about this, does it sound right? Please help as I have needed the defroster the past few days and I am burning up. Also it causes the windshield to fog up more before clearing it up. Thanks...Dean