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Matt
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 21713
Experience:  BEng hons Mech engineering, in auto industry 22 years
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2001 merc E320CDI . HI . WHEN MY CAR IS JUST TICKING OVER IT

Customer Question

2001 merc E320CDI . HI . WHEN MY CAR IS JUST TICKING OVER IT DRAINS THE BATTERY TO A NON START WITHIN 15- 20 MINS, BUT OVER 1100RPM IT CHARGES AT 13+ VOLTS. IF I TURN IT OFF AFTER A RUN WITH OR WITHOUT LOADS ON , IT WILL START OK . IT HAS HAD A NEW BATTERY AND ALTERNATOR FITTED ALREADY . CAN YOU HELP
Submitted: 3 years ago.
Category: Mercedes
Expert:  Matt replied 3 years ago.
Hello

OK this sounds like the alternator isn't being switched over to charge early enough

this is controlled by the ECU and is a function of engine speed and a electrical feedback / resistance loop

so 1st thing to check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright.


if this is OK then trace the small wire back from the alternator that runs into the loom and onto the ECU plug - check that the wire is undamaged and there's no corroded pins on the ECU plug or any other loom connections



If this is all OK then I'd consider sending the ECU off for repair / checking


http://www.the-ecu-doctor.co.uk/

http://www.bba-reman.com/uk/

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