The E320 in that year range upto approx 2005 uses an auxiliary battery to operate the brake pump when main battery supply was lost or low. The low battery warning you describe can be caused by the aux battery being low. This battery is a small 7Ah battery mounted under the pollen filter in the engine area.
Your best bet would be to join a Mercedes forum in the UK or in America this is free along with the information that you will get. I found them very helpfull .And i know they will help you solve your problem .I have made a note of your email address .I will contact you Trev
FIRST Reduce electrocution risk by disconnecting all power
supplies from the CD player and make sure any electrical charge has been
removed. Method 1
Take a blank/useless CD (such as AOL free trial CD's, you
can get them in a plethora of amounts in Best Buy) and place it about 1
inch deep into the slot.
Press the 'Eject' button and gently wiggle the CD around. If this doesn't work, repeat and try to get the blank CD below the the jammed CD, and gently pry the target CD upwards.
Get a 1 inch to 2 inch wide putty knife and wrap tape around it with the sticky side of the tape on the outside of the knife.
Use a strong tape like Gorilla tape for best results. The knife is
typically tapered so that if you wrap the tape tight enough it will not
slide off the end
Get a piece of paper and stick it to one side of the knife. Trim with scissors. You now have a thin sticky knife you can slide into the CD player opening
Insert knife into CD player with sticky side down trying to get it to go on top of the CD that is stuck. Press down gently to get the tape to stick to the CD.
Gently lift up and pull the knife out. Hopefully the CD will come with it. You might try hitting the eject button if it doesn't work the first time.
Get a stiff plastic "card" - like a drivers license but a bit thinner. Put double-sided scotch tape on one side of the card, near the edge of one of the two narrow ends of the card.
Get a thin-stemmed flat head screwdriver (short is better).With the sticky side of the card facing down, stick it into the **** ABOVE the stuck CD.
You may have to use the screwdriver to ensure the card goes in above
the CD and does not stick to the CD until after you get 1/2 to 3/4 inch
of the card in above the CD.
With the card still in there, insert the thin flat screwdriver ON TOP of the card and gently press down on the card. This causes the tape on the bottom side of the card to stick to the top side of the stuck CD.Remove the screwdriver and then slowly pull the card out. The CD should come with the card.
Check out this youtube viedo for a first hand look at what to do.
SAE is the rating of the viscosity of an oil.. So its the code that comes after the letters "SAE" that's important.. For instance my car requires "SAE 5W-20" oil. It's the 5W-20 part that is important.
To check this remove the earth wire on the battery and connect an amp meter in the circuit. If the current draw is less than 1 amp ( even that will be excessive for instruments ) the battery should last 48 hours . I would be checking for a heavy current draw indicating a unit shorting out internally or a battery that has an internal short problem. Have a load test done on the battery to check this. Clocks and speedo and odometer always use power after being switched off as that is how they keep time and mileage recordings so the current draw is in milliamps. Even the ECM draws power when off as that is how it keeps the CPU program going and why sometimes the problems start when the battery is changed out or disconnected.