Cadillac a/c controls

I have a 1988 Fleetwood d'Elegance in excellent condition. It has 107000 actual miles and I have maintained it mechanically including replacing the air conditioning to run the "new stuff." Now the controls to put it in automatic mode will not work. The a/c, when it has worked, is excellent. The GM dealer has literally replaced everything except the controls but they worry that may not fix it, and it is expensive. Does anyone know a solution to this problem, or experienced a similar problem.

So, exactly what is is doing or not doing?

Thanks for reply, maxwedge.

When I go to "auto mode" on the a/c controls I get the Service A/C light and the control defaults to "Econo mode". The A/C does not run. I had it serviced because of this problem a few weeks ago and the GM delearship that replaced the entire a/c system said there was no reason it would not run and infact it was running when I picked it up. That lasted for about 3 miles. I changed the temp setting and the a/c adjusted. However, about five minutes later it kicked out, got the "service A/c" light and it went to "Econo mode" and would not go back to auto. I took it back to the GM dealership. They checked it again and said it was full of coolant and the only things left we have not changed are the head controller and the engine computer. They found a head controller but don't want to just change it because the part is $390. I am looking for somebody who may be familiar with such a problem and a possible solution. I sure hate to give up on the old lady. It has served well and rides better than any new car I have been in. Everything else works fine such as the load leveling function.

The bcm reverts the system to econ when, one reason, it gets info from an ac pressure switch that says the pressure in the system is too high or too low, they can check this by going into diagnostics and looking at the readings from these pressure sensors. This would be always be done for basic diagnostics for this condition, seems to me they owe you at least a definitve diagnosis after all the work done! Caddyinfo.com has the obd procedures and code definitions.

Thanks, maxwedge. I am on my way over to the GM dealer right away.