Sorry for the delay in replying.
First of all, check the coolant level in the radiator and the overflow reservoir. Be sure the radiator is full and there is some coolant in the reservoir. Next, do you have a temperature gauge on the dash, and is it reading normally when the engine is warmed up? If it's reading lower than normal, suspect a defective thermostat. If you replace it, the cooling system must be burped to get the coolant to flow. After restarting the engine, remove one of the hex plugs or one of the temperature sensors on the thermostat housing, then refill the radiator. Failure to do this will prevent hot coolant from touching the thermostat so it won't open. Engine overheating will result.
If the temperature gauge reads normal, feel the two heater hoses after the engine is warmed up. They should be too hot to hold onto for very long. If they are, there is a problem with the temperature door in the heater box or the cable that controls it. Be thankful you don't have a newer car with unnecessary, over-complicated, unreliable computer controls that run the heater. Big bucks to repair those.
This can be a little hard to tell, but if you think the temperature selector lever doesn't feel right, the cable could be slipping. I don't know how the cable works on your car, but on the early to mid 1990s minivans, the cable passed through three fingers on the temperature door actuator lever. In one direction or the other, the door would reach its stop, and the cable would then slide through the fingers as you continued to push the control lever to the end of its travel. At that point, it was properly adjusted. If the metal pivot pin for that door gets rusted, the door won't move. The cable will just slide back and forth through those fingers making you THINK you're adjusting the temperature. This problem usually shows up this time of year after the door has been left in the cold position all summer, and has time to get rusty.
If the heater hoses are cool, suspect a plugged heater core. Back flushing with a garden hose usually clears them out. Be aware though that sometimes the sediment is blocking a leak caused by corrosion, and flushing the system will make that leak show up. Also, don't use a lot of pressure from the hose. The cooling system is only designed to withstand a little over 15 psi of pressure.
Wednesday, December 9th, 2009 AT 2:36 AM