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Marty
Marty, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 54142
Experience:  Bosch Certified Master Technician with over 35 years experience in the automotive industry.
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Sl55 amg electric consumer offline warning. has been an

Resolved Question:

sl55 amg electric consumer offline warning. has been an ongoing problem.large fuse replaced improved but didnt fix it.fault codes found and reset,no change. consumer battery showing a healthy 18.5volts with engine running so alternator not a problem. with engine off for two hours battery still shows 15.5volts which should be enough to run the systems however nearly all the systems have shut down until car is started [using starter battery]when systems start coming online again. after about an hour warning goes off and everything is fine until next day. i would suspect the battery is not holding charge but shows that it is [15 to 16 volts] the car seems to think there is not enough power to run the various systems so closes them down but there is enough AAAAAAARRRRRGGGHHH PLEASE CAN YOU HELP I do not want to start throwing ludicrously overpriced mercedes parts at this until i am sure what the problem is.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is ***** ***** is way too high. It sounds like you have a voltage regulator fault. You should get the vehicle scanned for fault codes with the Mercedes tester. More than likely you will find fault codes for excessive voltage, not undervoltage. You will probably need to replace the voltage regulator or alternator to remedy this problem.

Customer: replied 1 year ago.
ok but would this excess voltage cause the systems to go off. With 15 volts available after a short while with the engine off the doors wont unlock and there is barely enough juice to cancel the immobiliser
Customer: replied 1 year ago.
why wont this send
Expert:  Marty replied 1 year ago.

Overvoltage will cause the systems to shut down the same as undervoltage. What you are describing sounds like a weak battery though. What do you mean when you say there is barely enough juice? Is the rear battery going dead?

Customer: replied 1 year ago.
no the rear battery allways shows afull charge. by juice i meant that there is not enough power to run anything after a short period when the engine is off but the battery still shows a good charge. If the overcharging caused the systems to shut down why would they recover when the engine is running.However if you are sure there is too much charge then i will start with voltage regulator. I told this is a tricky one four engineers have failed to fix this problem
Expert:  Marty replied 1 year ago.

When an overvoltage situation occurs the system will shut down to protect them from damage. You need to get the voltage down to the proper range. 14.7V running is about as high as it should ever go.

Customer: replied 1 year ago.
ok thanks ill get the regulator changed and see what happens
Expert:  Marty replied 1 year ago.

You're quite welcome. Let me know if you need anything else.

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