CLK Alternator issue

SteveB73

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Hi all,

I have a 2004 270cdi which i have been getting the battery warning visit workshop message.

I have changed the battery as it seemed to crank slowly anyway, but did not put the message out. I thought process of elimination it must be the alternator, which i thought was strange as it was reading 14.5V with engine running, but thought maybe while driving the voltage regulation is not working.

However, after having an alternator fitted the garage has just called me to say its all fitted and the light is still on :-(

£600 in so far could use some helpful advice as to what to look for now..

Thanks in advance.

Steve.
 

Wighty

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I think reading the cars fault codes will narrow down any issues . Ideally using MB Star computer at an Indy (it will be cheaper than main dealer ) .
May be as simple as Glow plug relay , but get the codes read first
 
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SteveB73

SteveB73

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the garage said they plugged it in when the light remained on and got no codes reported..?
 
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SteveB73

SteveB73

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Is there a separate voltage regulator on these?

I've seen regulators on ebay but MB didn't seem to know anything about them when I called about an alternator? I kind of assumed the regulator would be part of alternator itself.
 

alexanderfoti

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Measure the voltage when running on the new altnerator.

I have had aftermarket alternators charge the car, but give this warning, as they take too long to start charging (a E220 CDI w210 had this fault, it would start charging 15 seconds after engine start).
 
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SteveB73

SteveB73

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its charging (according to the diagnostic mode in dash) at 14.2V-14.3V which remained steady at idle and revving the engine..
 

AMGeed

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I have just had a new alternator fitted to my E55 and it now charges between 14.2V and 14.8V.
The old one which finally packed in only charged at 13.4V - 13.6V max when it was charging the battery.
 
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SteveB73

SteveB73

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i also checked for engine management codes with my own machine just to confirm what the garage had told me and it reported no DTC's.

So frustrating as I am missing days of work as I'm reluctant to drive it in case it breaks down on route.
 
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SteveB73

SteveB73

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Quick update. Light is still on. The dash is showing 14.5V while driving. However I did notice as I pulled into the car park at work today that it dipped to 13.8V briefly.

Do you think this would be enough to put light on? What could possibly cause this?

Does anyone know if the alternator connected directly to the battery or do the cables go into something else first that measures / distributes the voltage?

If anyone has a wiring diagram of the relevant system I’d be very grateful :)
 

Steve@Avantgarde

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The alternator has a signal wire, terminal 61, that goes to the front SAM. Those wires break, on 270s its especially common as the wiring rubs on the intake pipe. To give you a clue, there is a 2 or 3 pin multiplug in the back in the back of the alternator, follow that wire, you will find a break in it somewhere.

The alternator is charging. 13.5-14.8v is charging spec.
 
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SteveB73

SteveB73

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Thanks for that. I felt sure after replacement and the issue persisting there must be something like that. Just didn’t know what to look for. I’ll have a look Saturday and update
 

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