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sprinkles08, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 22363
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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06 ml350 battery dead, replaced with smaller battery to get

Customer Question

06 ml350 battery dead, replaced with smaller battery to get to shop, Unit started, got big new battery but voltage 10 volt on new battery so friend put charger on battery under seat and crossed post wrong. Now powers up but no cranking over engine
JA: Did you test the battery with a voltmeter? And have you ever changed one before?
Customer: Yes
JA: Are you fixing your ML350 yourself? What have you tried so far?
Customer: Yes, own a shop but have not done many merc.
JA: Anything else you want the mechanic to know before I connect you?
Customer: That is all
Submitted: 7 months ago.
Category: Mercedes
Expert:  sprinkles08 replied 7 months ago.

Hello and welcome to JustAnswer!

Reversing polarity can instantly damage any electrical component or module. It's possible that some fuses have just blown but there may be much deeper damage.

The first thing you'll need to do is check all fuses and replace any that are blown. If the replacements blow then components on the affected circuits have been damaged.

If no fuses are blown or if there are still problems after fuses are replaced then a scan tool is going to need to be used to first see what modules do and don't communicate and see what fault codes are set. If it won't start then odds are the engine controller is not awake. It may have failed, if it's powers and grounds are present but it doesn't communicate then it will need to be replaced.

Customer: replied 7 months ago.
Checked fuses none blown
Customer: replied 7 months ago.
Will not be with car now until Monday at 8 am Atlantic standard
Expert:  sprinkles08 replied 7 months ago.