My ac on the driver's side of dashboard and back seat suddenly started blowing hot while the ac was one and the passenger side remained blowing cold.
AC problem in 1998 eldorado touring coupe cadillac on 1998 Cadillac Eldorado
You need an Air Conditioning System and Climate Control Diagnosis. Here is an article to help you or the shop with that process.
I've had the same problem on mine. For the drivers side remove the plastic pannel at the rear of the glove box reach in and move the lever from right to left for cooling and left to right for heating. For the pasenger side find identical arm below glove box by removing simple panal. Cheers.