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2006 S500 103k miles. I was driving home the other day and…

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2006 S500 103k miles...

2006 S500 103k miles. I was driving home the other day and the red battery charge message appeared. I parked it and it sat there a few days because of a snowstorm. It would then start but quickly give the red message again, along with SRS not working. After a few starts, it would no longer crank. Not running, the voltage across the battery was 11v or so. When running it dropped to 10.5v.The alternator is turning freely and I found no loose connections. I tapped on the alternator and the regulator with a wood block in case brushes in the regulator were stuck.I removed the battery, which is an MB one and looks fairly recent, and hooked it up to a charger. With the charger off, it now reads 12.7v. I've uncovered the prefuse in the passenger footwell but haven't tested it or removed it.I plan to put the battery back in, probe the prefuse up front for 12v, and pull any scan codes.

Mechanic's Assistant: Have you checked the battery, particularly the terminal connections? Are they corroded?

Yes, they're clean.

Mechanic's Assistant: Are you fixing your S500 yourself? What have you tried so far?

It's in my first post.

Submitted: 7 months ago.Category: Mercedes
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Answered in 1 hour by:
12/16/2017
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago
Wolfgang
Wolfgang, Mercedes Technician
Category: Mercedes
Satisfied Customers: 5,219
Experience: master tech benz ase cerified L1 and L2
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Hello I’m Wolfgang. I do need a vin # to get the factory information to assist you. Thanks
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Customer reply replied 7 months ago
Here is the VIN WDBNG75J36A479818, and an update on the situation;I put the battery back in after charging it. However, the key will no longer turn in the ignition switch, the steering wheel is locked as is the shift lever in Park. The dashlights work, as does the radio. The key fob will not lock or unlock the doors.That was yesterday. Today I disconnected the battery ground for 10 minutes and then reconnected it. That made no difference. Then I hooked up jumper cables, which raised the voltage across the battery from 12 to 13.7. That did not help.As of now the car is immobilized.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago

under the rear seat is the rear SAM module . is there any water leaks back at that area?

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Customer reply replied 7 months ago
There are no water leaks near the rear SAM or anywhere else. I will check the fuses in the SAM; could be one or more blew when I reconnected the battery. If so, that might unlock the ignition and the transmission. I'll get back to you after do that.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago

is it possible you hooked it up backwards first then corrected it?

mistakes happen!!

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Customer reply replied 7 months ago
No, Due to the location of the battery terminals and the shortness of the cables, it's not possible to connect the cables if it's in backward. Stand by until i check the fuses.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago

just making sure because the battery may be the same but the terminals may be reversed on the battery itself!!

seen that a bunch of times!! especially aftermarket battery!!!

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Customer reply replied 7 months ago
It/s a Mercedes battery, per my earlier post. I took it out to charge it, then reinstalled it.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago

sorry for my delay !! did you find out if any of the larger size fuses failed? in back and front ?

thanks

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Customer reply replied 7 months ago
not yet. I tried to check this morning but the fuse puller tool in the tire well doesn't work well on the fuses in the SAM.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 7 months ago

needle nose pliers!!

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Customer reply replied 6 months ago
Finally got it started. Fuse 78 would blow instantly. It's 7.5 amps but it blew 10a and 15a but 20a was ok. So an extra 10 amps is coming from somewhere. Once started, the battery was not charging which was the original problem. Likely the alternator/regulator.
Mercedes Mechanic: Wolfgang, Mercedes Technician replied 6 months ago

let me double check on the correct fuse amperage on 78

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Mercedes Mechanic: Wolfgang, Mercedes Technician replied 6 months ago

ok that is the correct amperage and that feeds the alarm horn/siren assy . so the alarm horn assy needs to be replaced. now with the no charging issue

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Mercedes Mechanic: Wolfgang, Mercedes Technician replied 6 months ago

the front sam controls the alternator. first check the fuse under the rf carpet make sure the 150 a fuse is not blown.

let me know

thanks

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