1999 Saturn heating problem 1.9L?

I am having problems with my car heating and defrosting the windows. The engine temp gage is at the 1/4 mark and is normal like it always has been. I replaced the thermostat but this had no affect on the problem. Still very little heat coming from the blower. Any ideas what my problems are? It seems I get a little coolent flow but not the full amount. Is there some valve in the system that is not working? The system uses dex-cool so I do not think the heater core is plugged. Any help or ideas would be great thanks.