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Old 22nd July 2017, 14:59   #1
pevil
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Hey guys & gals,

As title says this is not a 75 question but hopefully one of you knowledgeable people may be able to help, wife's Smart ForTwo has a charging problem, at tick-over (with multi-meter on battery terminals) I'm reading 14.2v, increase the revs and it drops to 12.6v and so on, turn side lights on and it reads about 14.2v all the time, this happens while travelling, throttle open 12.6v throttle closed 14.2v, lights on 14.2v throttle closed or open, changed battery, no difference, I know the alternator is controlled by the computer but this scenario is causing the battery to go flat!

Any ideas before I spend a load of money at Mercedes getting it on the diagnostic
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Old 22nd July 2017, 15:40   #2
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I'm pretty certain this will be an alternator problem Peter. 12.6 volts is inadequate to charge your battery. Buy an exchange alternator from a motor factor and get it fitted by someone cheaper than a Mercedes main dealer!

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Old 23rd July 2017, 09:09   #3
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Hi.
A friend of mine on one of the vintage radio forums had exactly the same issue. A new alternator was tried to no avail and eventually Mercedes diagnosed a computer issue, now I think it was the body computer at fault, the price was eye watering, eventually he obtained a second-hand part but it was expensive to get it coded into the car.
I can only say good luck and fingers crossed it is just the alternator and not the computer. The regulation is done in the computer not the alternator allegedly.
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Old 27th July 2017, 16:21   #4
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Quote:
Originally Posted by SD1too View Post
I'm pretty certain this will be an alternator problem Peter. 12.6 volts is inadequate to charge your battery. Buy an exchange alternator from a motor factor and get it fitted by someone cheaper than a Mercedes main dealer!

Simon
Quote:
Originally Posted by murphyv310 View Post
Hi.
A friend of mine on one of the vintage radio forums had exactly the same issue. A new alternator was tried to no avail and eventually Mercedes diagnosed a computer issue, now I think it was the body computer at fault, the price was eye watering, eventually he obtained a second-hand part but it was expensive to get it coded into the car.
I can only say good luck and fingers crossed it is just the alternator and not the computer. The regulation is done in the computer not the alternator allegedly.
Thanks guys, I hope it's just the alternator or connections but with the accelerator sensor acting like a switch it could be the SAM unit, HOPE NOT.
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Old 27th July 2017, 20:27   #5
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Would a temporary cure be to drive with the lights ON so that your battery will be getting charged.

It won't hurt the car to run with the lights on. Lots of cars do just that for increased visibility and safety.----
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Old 8th August 2017, 21:10   #6
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Peter.---How are you getting along with that charging problem ???
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