Thanks for the ideas and the feedback. Unfortunately, unless I messed
> something up along the line (which is certainly possible), I think I
> have already eliminated most of the ideas. I guess I forgot to
> mention, but the thermostat was changed a couple weeks ago. That
> seems to be working fine. The coolant level is OK. The blower motor
> is OK; it is definitely moving air. The temperature gauge stays at
> the 1/3 mark regardless of whether the car is sitting there or
> moving.
> Jim suggested perhaps there is a vacuum leak in the system that
> controls the doors that regulate airflow. I have not really noticed
> anything strange about the operation of the system. It does not seem
> to be slow to respond, but I have not really been thinking about it,
> either. I will try to do some research on this. In the meantime, if
> anyone has ideas on how to definitively determine whether this system
> has a problem or not, I'd be glad to hear them. Thanks much!
> - Phil