I just bought a 2002 Eldorado ETC with what I was told was just one problem: the climate control does not work. I.E. the display comes on for a few seconds when you turn the car on, then it just shows two dash lines on the left and right. Additional problems, no sound or buzzer when you don’t have the seat belt or when you leave the key in and open the door. the power door locks don’t lock, no cabin lights. the power antenna does not go up and no high beam and most of the time the blue high beam light will not go on. HELP! ALSO I played the CD for just a short time without the engine on and it would not start the next day. Said the voltage was 9.7 volts. I "know why did you buy it! I even drove it 600 miles from Ca. to Salem Oregon with no air in temperatures of over 100 degrees. It drove like a dream, and get this. MPG was 30 unreal but true. Like I said in the title She had me at “HELLO!” I CALL HER RUBY, RUBY RED.
At the least it sounds like you need a new battery, a voltage that low indicates a dead cell. Trying to charge a dead battery will kill an alternator in a short time. I suggest reading the Owner’s Manual from cover to cover. It may help diagnosing some of the issues.
Actually I would start by checking all the grounds, starting with the engine to chassis ground straps, then the ground points under the dash. Could be this thing was in a flood at one time and all the grounds have corroded.
As already suggested, have the battery, the charging system, and the grounds & battery cables checked.
Beyond that, is sounds ilke there’s a problem with the Body Control Module. Start by checking all the fuses, then visit your owner’s manual, and if needed you can have the dealer look at it and see if the BCM protocols can be reinitialized.
By the way, if you do find a blown fuse and replace it and the new one blows also, STOP THERE. That’ll mean you have a short somewhere.