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The blue wire in the back of the alternator has no power…

The blue wire in...

The blue wire in the back of the alternator has no power when the key in switched on,after replacing the battery in 2003 benz s430 4matic so the alternator is not chargong

Mechanic's Assistant: Have you changed a battery before?

Yes

Mechanic's Assistant: What is the model of your '03 Mercedes?

S430 4matic

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

My problem is to know how to get the charging system out of switched off mode

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Answered in 16 hours by:
11/16/2017
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 5,490
Experience: 15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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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!

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you do not get 12 volts from the wire, you get 12 volts from the alternator when the engine is running,

have you checked it while its plugged in?

have you verified you have battery voltage when the engine is off on the big positive wire at the alternator?

Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 5,490
Experience: 15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
Verified
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Customer reply replied 3 months ago
thanks for the tip Dude ,I am going to replace the alternator today because my info about testing the blue wire was wrong:i was testing it disconnected from the alternator with key on,but I got no 12v.
Customer reply replied 3 months ago
I replaced the alternator and the problem was solved,thanks again
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Lou P. master tech
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
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