Heater Air Control Vents Closed
My 84 300TD heater and blower appear to work properly based on small amount of very hot air and loud blower noise, but air control door(s) close when I turn heat on. Everything works perfect for air conditioning. Have very infrequently had same problem with air conditioning for years, but always cleared up after stopping car and letting it set for a while.
Have taken it to 2 dealers and 2 independent MB specialists and they all say very expensive and no guarantee they can fix the problem. It is clear they do not want to attempt the job.
Climate control has never been worked on by anyone.
Any help pinpointing the problem would be appreciated.