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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22744
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a c320 that has the battery/alternator ligjt on.

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Hi I have a c320 that has the battery/alternator ligjt on. It has had a new recon alternator and new battery. And again the light has come on. I have had the battery and alternator tested at three different places and all say that they are both fine. So I'm at a loss

the alternator is switched over to charge by the engine ECU so 1st thing to check is the condition of the small diameter wiring from the back of the alternator as the diode pack of the alternator is controlled by this wiring

Ideally disconnect the ECU from its sockets and have an auto elctrician do a continuity check between the ECU pins and the alternator wiring

if the wiring is OK then the ECU will need to be repaired

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Customer: replied 3 years ago.

Hi car has been sent into garage to have the ecu checked. So fingers crossed.