Have a 2003 SL 500 starts and runs fine so seems like battery and alternator are fine. Getting message "electrical consumers offline" Malfunction and several things not working while that error is present. any ideas

 

It is a feature of these vehicles that if they are not used regularly then to save power on first start up this display appears and all non-essential electrics are switched off and will not work until a preset amount of charge has returned to the battery. Usually this is within a mile or so of driving the car or just leaving the engine running for 5 minutes or so. You will probably find that things like the cruise control stop working until the display warning goes out. If you just use the car at weekends this can happen. If like some SL's it only get used a few times a month then the only way to avoid this is to fit the MB Battery optimiser and leave it connected to your car when not in use. They do a realy neat kit so you can fit it all in your boot semi-permanantly.