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Discussion Starter #1
Can anyone shed any light on why my battery light came on and my speedo stopped working at the same time, could this be a problem with the alternator as the voltage across the battery terminals when running is still 12 volts.
 

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I would say it's unlikely for it to be battery problem, because if you get battery problems you'll get a whole host of other errors ... can't help you apart from that I'm afraid ...
 

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Discussion Starter #3
Cheers it may be a coincidence that they both occured at the same time. The charging circuit is not working and I think the speedo comes from the ABS unit but i am not sure.
 

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The speedo feed does come from the ABS unit.
Is the ABS working?
 

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ok.
you know you have a fault with the ABS.
you need to fix that because it will fail its next MOT if it stays that way.
with the non working speedo, you now have a further reason to fix the ABS fault...
 

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Discussion Starter #7
I cannot understand why the battery light came on at the same time as the speedo stopped working, is there a fuse or anything in the same line, does anyone know where I can get a wiring diagram.
 

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I cannot understand why the battery light came on at the same time as the speedo stopped working, is there a fuse or anything in the same line, does anyone know where I can get a wiring diagram.
I don't think even alfa have a wiring diagram ;) :lol: ... seriously though I'd do as David C recommends ... the best thing to do is sort out the known problems first and then you can realistically start fully diagnosing the other faults ... (more often than not a single fault can have multiple symptoms ... even if they don't all appear at once)


Good Luck getting is sorted
 

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It may just be a coincidence.
But go through all the fuses and check them anyway.
Starting with the big fuses on top of the battery, one of which is the ABS fuse.

Have you checked the battery voltage?
you need to first check it without the engine running (and when it hasn't run for a while) then check it when the engine is running.
 

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Discussion Starter #10
I have checked the fuses on top of the battery, these are ok and the battery voltage is approx 12v not running and still 12v when running when it should be approx 14v. With my luck they are probably not related.
 

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I have checked the fuses on top of the battery, these are ok and the battery voltage is approx 12v not running and still 12v when running when it should be approx 14v. With my luck they are probably not related.
Sounds like there is a definite problem there then, it should be 14v when running, how old is your battery?? (worst case alternator???)
 

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ok.
so alternator not charging...

With it like that, do not drive it because you will get stranded with a flat battery very quickly.

Not sure what the common issues are with them on a 156, but loose connections are always an issue!

The alternator isn't easy to get to either, tucked down the back of the engine...
 

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Discussion Starter #13
The batteries ok, I think I'm going to have to check the alternator connections are ok and if it is getting 12v to the field terminal on the alternator, you are right its not in the easiest place to work on.
 

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I cannot understand why the battery light came on at the same time as the speedo stopped working, is there a fuse or anything in the same line.
Yes there is, the engine earth lead, I've seen this once before, the engine earth lead has not completely snapped but enough has gone and the battery has slowly drained, though it still thought it was charging, then the speedo dies because of the low voltage (if you check it with the engine running it should be 14.4V NOT 12V), so there are 3 things you need to check first, Battery is OK, Alternator is OK and the Earth strap, you still need to fix the ABS fault (probably a front wheel sensor), but that wont be the cause of this other trouble.
 

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Discussion Starter #16
Fixed the ABS fault, offside wheel sensor cable damaged, ok now. trying to remove alternator now but there is not a lot of room.
 

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Hi , I got almost similar problem. When I start my car , the speedo works fine. But, suddenly the ABS and hand brake ligts are on and then speedo is not working anymore?

Appreciated if any idea what could be the main cause of such problem.

Thanks
 

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the speedo is worked via the ABS system, if its faulty then the speedo will not work
 

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Discussion Starter #19
I found the fault with my speedo was the alternator. when the speedo sensed the voltage was low it stopped working. I had a abs light on but this was a wheel sensor this is now ok. If your wheel sensors and cables are ok it may be your abs unit as this is where the speedo supply comes from.
 
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