dash display panel needs rebuild
you need to replace the cluster..
The letter C on an AC display on a 91 Cadillac Deville means cold. It is often the coldest setting available.
uotside temp sensor in front of the radiator has gone bad
I believe fuses are in the trunk!
check fuses
what buttons are used to bring up codes on display of 1994 cadillac etc
there is a button near the spedometer display that switches us and metric
The wiring is wrong. Same thing happened to me and I replaced a relay cluster and fixed the wiring it's most likely the yellow wire or memory.
Hold the OFF and WARM buttons on the E.C.C. When 7.0. is displayed on the F.D.C press the HI button once, You should now see E.9.5 displayed on the F.D.C. Then hold the ECON and WARM buttons on the E.C.C. and the F.D.C should now display E.5.0 indicating your in override diagnostic mode and depending on what you want to do use the HI or LO buttons the scroll up or down.
theese are lit by a 16 volt output from the body control module we often find its a bad bcm.
push the AC and heater buttons in at the same time and hold for 6 seconds
Cadillac has the a/c to not blow cool air when there is a promblem, you need to get the codes of the car computer. turn the key on but don't crank the engine then push the off and warmer buttons together and the codes will display them selfs.