The two vents on the upper part of the central panel can be taken off. There are two prongs that need to be pulled in on either side of each vent. Once those are out you can see more screws.
Climate Control Panel
check fuses and for vac leak at unit and vac pump
GET THE HAYNES REPAIR MANUAL FOR THAT GROUP OF CADILLACS CH 6 HAS THRM ALL 86 to 90 Broughams were incapable of pulling DTC's through the climate control head. To perform a self diagnostics on them, you have to jump the terminals on th ALDL. Follow the instructions in the link to pull DTC's.
It is for dule zone climate control
The climate control module is part of the control assembly. The entire assembly has to be replaced as one unit for the 1990 models.
In order to get codes for a 1994 Cadillac STS through climate control, a diagnostic test must be run by a mechanic. Most alternative tests or guide books will not provide this information. A Cadillac dealer is the best option to obtain this code.
The climate control computer may be defective. Check all fuses. is the defrost cold air?
Should find ECM just under center dash below radio and climate control panel
Push OFF and HI together om the climate control panel and hold
press off and warmer buttons on climate control center. warmer is also the pass side heat button.
they just shot internaly i have a spare if you need it, wmarrs0549@yahoo.com
ignition on motor off then press and hold "off" and "rear def." for 10 seconds on the climate control.