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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4966
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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On a 2003 MB e320 sedan how can i test the K57/2 battery

Customer Question

on a 2003 MB e320 sedan how can i test the K57/2 battery relay and the battery control module. i have a new rear battery (main), a new alternator and an auxiliary battery that test as good on a load test but i have a drain on both batteries and have pulled all regular fuses one at a time on a isolation test to find a circuit that is "draining" but found none. i hate to buy the part without knowing if it is bad or not.
JA: How many miles are on the car? Has the car been starting normally?
Customer: 139k miles and starts okay but with "consumer electronics switched off" warning until it is driven for a while. if is sits for over one day the battery will drain and then it may not start, especially in cold weather.
JA: Are you fixing your E320 Sedan yourself? What have you tried so far? Anything else you want the mechanic to know before I connect you?
Customer: yes but have a great independent mechanic (only works on MBs) that i have used for almost 20 years through 3 MBs i have owned. I can't just leave the car with him until he gets time to try to anylize it. he and i have brained stormed and i can take it back to him if necessary. i trust him immensely, but he does not have all the expensive equipment. i avoid the dealership like a plague
Submitted: 9 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 9 months ago.

Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

Expert:  Lou P. master tech replied 9 months ago.

There are a few common issues with the W211 that cause excessive at rest current draws, usually its an audio component (amp, radio, sat radio module) other times its a seat or door module. can you tell me the process you used to check for the draw? doing a mercedes draw is a very specific process, you need to open all the doors and hood and trunk and then manually lock all the latches for the doors, hood, and trunk and then use tape or wedges to press in all the door jamb switches, then you insert the ammeter in series with the negative cable or use an amp clamp if you have one, then you lock the car and wait 30-45 minutes for the voltage to stabalize as the car will actually go to sleep and then if the measurement is greater than .050Ma you pull 1 fuse at a time until the draw stops, there are a few different fuse boxes, I will send over some pictures of the locations. Lou P.

Expert:  Lou P. master tech replied 9 months ago.

The mercedes info is slightly different then what I do but still the same results, it saves the steps of having to open all the doors again.

Expert:  Lou P. master tech replied 9 months ago.

here is all the fuse box info, hope this helps. Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.
Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.