I have a Eldorado Doral, year 2000 with a charging problem. The "Service charging system" message comes and goes. As the voltage drops the "Service ChargingSystem" woulddisplay, but it is now showing all the time.Ihavechanged the battery, I am on the second alternator and it tested good, but the charging system will not work at all now. Battery voltage drops consistantly. I have checked all the fuses, all checked good. All grounds are tight and checked for loose connections unless there are some connections I am not aware of. The message pannel displays a battery voltage increase with battery charger, however when I start the car with charger disconnected the voltage drops.Have run out of ideas as to what the problem could be or where to look next.
Thanks for any input on this...

 

Just grasping at straws but what about your belt and idle? Also just thinking that there has to be a draw somewhere. Under hood light, trunk light, are they turning off when closed? Any other power drawing accessories left on inadvertently or defective? Heated seats or mirrors?