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Discussion Starter #1
Hi all,

I'm a new 147 owner and have an odd issue.

I get a battery low message while driving and the car will eventually shut down.

If I put a tester onto my battery while idling it goes right up to 14v from 12v while off.

However it will gradually drop by about 0.01v every 5 seconds

The alternator, earth cable to gearbox, and starter motor have all been reeplaced and I have no idea what to do next.

FYI alternator was fitted by previous owner, starter motor by myself.

I'm stumped, any advice really appreciated
 

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Next, you should close car with opened bonnet, disconnect negative pole from battery and put amperemetre in serie ( in line ) between disconnected strap and negative pole. Better use crocodile clamps since it is needed to wait some minutes for current stabilizing.
This helps to understand leakage if any.
PS. What is a low battery message ???... Has battery symbol appeared ???...
 

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It means that you have no charge comes from alternator.
Surely strange it has appeared ontime.
I may admit service belt is not tight enough. Just a simplest guess.
Basically it is alternator problem.
:thumbup:
 

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I would have to contradict the theory that the alternator has gone, from what you say if the battery is showing 12v to start with and goes to 14 while running with alternator and then the battery starts dropping, then the battery is surely not charging because it's not maintaining charge. You will have to try another battery on the car to see if it's really the alternator. Alternatively disconnect the battery and check the voltage overnight if it doesn't drop voltage by the morning , then certainly the alternator could be the culprit.
An alternator can drain a battery while left connected and not running, because the diodes reverse and discharge it , say overnight, but similarly, will still charge while running normally.
 

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Discussion Starter #6
Thanks alfapat, I can confirm that charge doesn't drop overnight, and I have tried another battery too with the same result

It drops while the engines running, I'm beginning to suspect that the new alternator may not be correct, as looking at replacements online the amps vary, maybe this alternator doesn't output enough?
 

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You should get a reading above 12.6 v on the battery with the car engine off, it really should not move, if it does you have something drawing on the battery.

With the car running the voltage should be over 14v and stable.

Are all connection clean and tight?

Alternator check

Battery check
 

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Discussion Starter #8
Hi verbout,

Is the engine off check with the keys in ignition? I've been checking it with keys out of ignition and not turned
 

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Discussion Starter #10
Thanks verbout,

Just tested and no drop with keys out, or in for that matter. Only once engines running, it jumps up to 14 and slowly decreases
 

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Ok , in that case , check your fuses are ok and connections to them ok , and then you will have to check the connection at the rear of the alternator , before ruling it out.
It's a pig of a job to change and you need to be certain.
 

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I would remove fuses 1 by 1 and see if there is a specific fuse that makes any difference but, thinking about it, if the battery is good a current drain that high ought to blow any but the biggest fuse.

So, personally, I suspect there just might be a problem with the alternator when it is spinning fast that means that not only does it stop charging but it also draws current.
 

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Discussion Starter #14
Yea that makes sense.

If I buy a new alternator tomorrow, what amp should it be? Eurocarparts lists a few but they all vary.
 

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It might be the alternator, but was its pulley changed when the alternator was? There is a one way clutch in the pulley* which may be failing and progressively slipping as it heats up. Noise and/or heat from it would be indicators. If you can see the fan you might notice that its speed does not rise and fall with the engine speed. With the belt off you can check the one-way action of the pulley.

* At least on diesels, I'm not sure about the petrol engines.
 

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Yea that makes sense.

If I buy a new alternator tomorrow, what amp should it be? Eurocarparts lists a few but they all vary.
I don't think the solution is "parts swapping".

You need to find the problem before throwing parts at it....:tut:
 

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Discussion Starter #18
Thanks, i didnt know that about the pulley so I'll check that.

And your correct about parts swapping, its just through poor timing we are without a car despite having a few, so I need to get this one roadworthy as soon as I can, but your correct.
 

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Does the car charge when on idle or just above idle?

If so very slowly increase the revs and note at what rpm it ceases charging.

Repeat the tests a few times.

If it repeatedly ceases charging as revs increase then it reinforces alternator or pulley. I certainly didn't know there was a clutch in the alternator pulley but I have never had a close look at one on the 147.
 
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