Cadillac Repair: 83 DeVille ECM problem, diagnostic capabilities, electric component

Question
Hi, thanks for making this service available!  I have a 1983 Coupe Deville, with the HT4100.  It's kinda been my back-up car; I've owned several of these same models, so I know a little about them.  I will say that I have had long term (intermittent, however) problems with the ECC and Fuel Data displays going black (blank) and and subsequent loss of access to their controls and diagnostic capabilities; concurrent with the blower fan coming on by itself.  The problem usually, and eventually would correct itself, and I would again have my displays back and functioning control buttons to work with; and the vehicle runs pretty darn good during these good times.  Well, I'm currently dead-in-the-water, so to speak.  The displays have been blank for weeks now, and the ECM no longer appears to be controlling the HT4100; extremely sluggish performance; as if the injectors are flooding the motor with fuel; and/or the timimg seems as if it may be off.  I am not all that technical, but it is my gut feeling that there is a minor electrical problem somewhere.  It is somewhat my understanding that several components are tied together in some manner; these components being the ECC, the Fuel Data Center, the ECM, the computer that controls the plenum dampers, and an electric component located under the hood, with a large heat-sink on the bottom, that drops into the plenum, near the blower, and appears to control the blower operation, to an extent.  I've kind of "touched" most of these components, and feel that the problem may be with the computer-card device that controls the dampers.  Another observation; in the early days of this problem, it appeared to be related to (atmospheric) temperature, in that, if the car was hot, as after being parked in the sun, with the windows closed, this greatly increased the likleyhood of the problem occuring.  Often, this was remedied by parking in the shade, with the windows down, for an hour or so, and presto, back to normal.  Any ideas on this would be greatly appreciated!?  Thank You,  Ross STLSMO.

Answer
the computer that controls the plenum dampers IS CALLED THE PROGRAMMER.

an electric component located under the hood, with a large heat-sink on the bottom, that drops into the plenum, near the blower, and appears to control the blower operation is called the POWER MODULE.

Exactly what is it that the Ac does not do ?.