More confusion:

A variable I neglected to mention is that this car sat for 5 years in a barn. I got it this summer and this the first time the heater has been used. Part of this may be my difficulity in learning the mechanism.

This morning I had very good heat after about 5 min. at 20-40 mph. Operating temp was 60-70. As I got up to 65 in the interstate the operating temp increased to just about 85 and the heat went off. When I left the interstate the heat came back on and the operating temp decreased to about 75. At this pint I have very good heat around town but none on the interstate.

I think I will run it for a while longer before I make any significant changes. I wondering if the system just need to be used for a while.