Alfa 159 Battery Alarm???!!!! - Alfa Romeo Forum
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(Post Link) post #1 of 21 Old 11-05-19 Thread Starter
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Alfa 159 Battery Alarm???!!!!

Hi Guys, looking for some experiential advice before spending more money on alternators. I had to replace a failed alternator about 18 months ago due to steering fluid leaking onto it. Was a new aftermarket alternator. Reputable mechanic replaced it.
For the past 9 months, I've been getting the occasional battery warning alarm - typically within 30 seconds of starting. Checked battery voltage with engine running and it is about 14.2V. Battery is good. When not running, sits at 12.6V. When it occurred, if I stopped and restarted the car, the battery alarm typically went away.

Thought it was just my Alfa!

However, yesterday, the battery warning always came on, but not when idling - had to get rpm to 1500, then it comes on - always now.

Connected my OBD and recorded the RPM and batter voltage and have graphed it. Attached pic - blue is rpm - left hand scale, orange is battery voltage - right hand scale.

The battery voltage is staying between 14.21 and 14.37 all the time in measurements (albeit the interval is about 1 second, so something funny might be happening between readings that OBD doesn't detect). The battery alarm comes on every time as the RPM transitions thru 1500rpm and then says on regardless of RPM.

There are no faults reported by diagnostics.

So does anyone have any advice as to what is happening here? I don't want to replace the alternator if its ok and the problem is elsewhere (it is a bugger of a job and I don't want to do it myself, so it gets expensive).

And I don't want to leave it and then find myself stranded with a failed alternator if that is the case.

Advice on next course of action to determine what the issue is?

Regards and TIA.
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How old is the battery?
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How old is the battery?
less than 4 years.
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Most cars, i'd say the battery would be fine......but these eat batteries like nothing else, probably due to the constant drain?
Time for another new battery I think.
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Most cars, i'd say the battery would be fine......but these eat batteries like nothing else, probably due to the constant drain?
Time for another new battery I think.
Well, I have another battery that I can temporarily fit to see if the problem goes away. It doesn't have the CCA to leave in, but it should rule out the battery as the cause if it keeps occurring. If it still happens then ....??
Why would it be behaving in this strange way related to RPM? It is absolutely repeatable whether hot or cold. Not sure how a battery would cause these symptoms related to revs?
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One thing people don't understand about batteries is that they also act like large filter capacitors and remove noisy ripple from the 12v supply. You have to realize is that you are no longer driving a car, but a small Local Area Network with several computers packaged together that just happen to have a couple of wheels underneath to get it around.

Just make sure the replacement test battery is newish, in good condition, and fully charged. At least it costs nothing to give it a try.
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Put another earth strap on too.....even just to rule out a poor earthing that's happening under vibration
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Put another earth strap on too.....even just to rule out a poor earthing that's happening under vibration
Tried the different battery - ran a full charge overnight to ensure it was fully charged. No difference - still get battery alarm come on as the revs pass thru 1500.
I've checked all connections for poor connection - retightened and used voltmeter and ohmmeter to check for any bad joints. All sound.

Given it is now absolutely repeatable and occurs at exactly the same revs, it does seem to me to be electronics in some way - either the rectifier on the alternator or the sensing electronics for a bad alternator in the engine or body computer or instrument cluster. Thats the problem with a local area network of computers on wheels - isolating the problem!

So, apart from it being a faulty alternator, does anyone have any other suggestions?

I'm working thru elearn to check how the circuits operate to generate the battery alarm to see if there is anything there. I guess my issue is what else might be causing a false report?
As a temporary workaround, I'm going to fit a voltmeter so I can just monitor the voltage while the alarm is active so I know if the alternator does crap out - before the car stops working due to flat battery - never a pretty experience - watching all the failure alarms go off progressively as the battery dies is unpleasant!!

Hopefully, someone can give me further leads to rule the alternator in or out as the problem. I don't want to spend $1200 replacing an alternator to have the problem still there!!!
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Ok - here's an update. Checking elearn there is a small wire from the alternator that goes to the body computer that is used to determine if the alternator is charging. According to elearn, it comes into play at 700rpm plus.
So, I disconnected the wire and started the engine - the battery alarm went off immediately.
So I'm going to guess there is something failing on the sense circuitry of the alternator that produces the signal for the body computer. Thoughts?
So maybe the charging circuitry is ok and the problem is in the sense circuitry. Whether that is a portent for future problems its not clear.
But with the voltmeter connected in the interim, I should be able to at least monitor the charging in the near term. Hopefully, its not urgent to replace. Pity the circuitry on the alternator can't be changed without taking the alternator out (I think the turbo is too close)- because a replacement rectifier is only $40. OF course - unless someone has done it in situ and can tell me how they did it! I'm all ears if you can advise!

Here is the elearn extract:
Operation
With the alternator still with the ignition key in the ON position, the Body Computer lights up the warning light in the instrument panel and sends a power supply to the voltage regulator built into the alternator via terminal D+.
In these conditions the energizing circuit (rotor) is enabled to earth by the regulator electronics.
With the alternator rotating through the effect of the variation of the rpm and the magnetic field, a three-phase alternating voltage is produced in the electrical circuit (stator) which rectified by the diode bridge can exit terminal B+.
When the upper fixed calibration level (13.7 - 14.2 V) is reached it charges the battery and supplies the system.
The Body Computer checks the efficiency of the alternator recharging system by detecting two parameters: the voltage signal coming from terminal D+ of the actual alternator and the engine rpm signal received on the CAN from the engine management control unit
At the key-on as long as the voltage is below around 5.5 V, the Body Computer signals the insufficient recharging state; when the voltage exceeds 5.5 V, the warning light goes out; if, on the other hand, with the engine moving (speed above 700 rpm), the voltage decreases below the level of 4.5 V, then the warning light comes on constantly accompanied by the display of a message.


Any further thoughts?

Last edited by m282; 12-05-19 at 05:10.
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Pity the circuitry on the alternator can't be changed without taking the alternator out (I think the turbo is too close)- because a replacement rectifier is only $40. OF course - unless someone has done it in situ and can tell me how they did it! I'm all ears if you can advise!
Voltage regulator can be replaced in-situ by removing the down pipe next to it.

I would suggest taking it to an auto sparky who can hook up the system to a diagnostic CRO. A half hour with a sparky may be smarter than replacing parts on a guess.
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Voltage regulator can be replaced in-situ by removing the down pipe next to it.

I would suggest taking it to an auto sparky who can hook up the system to a diagnostic CRO. A half hour with a sparky may be smarter than replacing parts on a guess.
That is what I was thinking of doing - it needs a data logging voltmeter/ CRO with memory to determine precisely what is happening and confirm the problem is in the alternator and not the body computer (which seems unlikely). Wish I still had my job and access to this sort of equipment. It would be good if the problem is the rectifier and if it can be replaced in situ (albeit looking at the turbo, taking off the upper pipe still doesn't clear the lower part of the alternator as it is very close to the turbo body, so I don't know whether its possible to get at the nuts holding it on and then pull the rectifier clear) - have you done this on a 2.4?
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You only want to replace the Voltage regulator, not the Diode Pack (rectifier)

But as said, take it to a sparky first, while new alternators are very reliable there IS a reason why they have warranties.

HAVE you checked all the earthing straps and points?
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You only want to replace the Voltage regulator, not the Diode Pack (rectifier)

But as said, take it to a sparky first, while new alternators are very reliable there IS a reason why they have warranties.

HAVE you checked all the earthing straps and points?
Correct - it is the regulator that seems to be the problem - didn't mean to confuse with my shorthand. I've checked the key earth straps in the engine bay - all are good and showing no voltage drop or resistance. Trying to find out if a replacement regulator is available from Alfamen - but I'm not hopeful. None of the local auto electricians have a CRO/ Scope - of course. So there seems only one way forward.....
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They are available on eBay.
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None of the local auto electricians have a CRO/ Scope - of course.
REALLY ? !!

You need to find a better class of Auto Electrician!
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They are available on eBay.
Yes, I saw that - there are some interesting oscilloscope devices available these days. Tempting to get a low cost one as there are always occasions when it could be useful - but not enough to spend considerable $$. Getting the right price point that is both affordable and flexible enough (e.g automotive thru to domestic ac) is a challenge.
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No, I meant the Voltage Regulators are available on eBay!
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No, I meant the Voltage Regulators are available on eBay!
Yes, I saw that too! LOL! But they specifically say they are for Denso - at least the one I looked at - and given the alternator I got from Alfamen is 'unbranded', its not clear if there would be any issue - there shouldn't be given that it is just about exciting the stator, but I'd need to confirm.

Simplest is if Alfamen could supply one.

Again, I'm told that it is not possible to replace in situ, so it may just be theoretical as if I have to pull it out, then I will get an OEM and be done.

There could be a used Alfamen alternator with regulator issue coming on eBay soon....

Update: As of this afternoon, the alternator has completely failed. No longer charging at all. So clearly the regulator has completely failed and who knows if the rectifier has also failed.

And Alfamen won't take any responsibility for the alternator. Best not to buy from them.

Hopefully the Magnetti alternator will be a better result.

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So now have a new working alternator in the 159 - Magnetti Marelli. Hopefully this will last longer than the unbranded stuff Alfamen supply. Unimpressed - but not surprised - by their lack of communications to a customer.

Took the alternator apart - nothing obvious, the regulator is completely sealed - however one side where it was screwed down was loose - even though the screw was very tight. So perhaps vibration killed the regulator.

And another piece of information for those who might consider trying to change the regulator and/or the rectifier without removing the alternator. YOU WON"T BE ABLE TO DO IT INSITU! You must remove the alternator. The screws/ bolts holding everything in place are extremely tight - you could not undo them insitu as you could not get the pressure/ angle to turn the screws - particularly those on the regulator. Secondly, everything is soldered, so getting to the solder joints and desoldering then resoldering in place is just not possible. Finally, to get the regulator out, you need to remove the brushes to the rotor rings - and putting those back on insitu is just not possible. IF you have the alternator out of the car, it would be a 10 minute job to change the regulator and a 30 minute job to change the rectifier plate.
But then of course, you need to check it all works - a little challenging without putting it back in!!!

Hopefully this will help someone in the future. Battery Alarm means an alternator failure/ near failure. Don't waste time on chasing rabbits!
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So now have a new working alternator in the 159 - Magnetti Marelli. Hopefully this will last longer than the unbranded stuff Alfamen supply. Unimpressed - but not surprised - by their lack of communications to a customer.

Took the alternator apart - nothing obvious, the regulator is completely sealed - however one side where it was screwed down was loose - even though the screw was very tight. So perhaps vibration killed the regulator.

And another piece of information for those who might consider trying to change the regulator and/or the rectifier without removing the alternator. YOU WON"T BE ABLE TO DO IT INSITU! You must remove the alternator. The screws/ bolts holding everything in place are extremely tight - you could not undo them insitu as you could not get the pressure/ angle to turn the screws - particularly those on the regulator. Secondly, everything is soldered, so getting to the solder joints and desoldering then resoldering in place is just not possible. Finally, to get the regulator out, you need to remove the brushes to the rotor rings - and putting those back on insitu is just not possible. IF you have the alternator out of the car, it would be a 10 minute job to change the regulator and a 30 minute job to change the rectifier plate.
But then of course, you need to check it all works - a little challenging without putting it back in!!!

Hopefully this will help someone in the future. Battery Alarm means an alternator failure/ near failure. Don't waste time on chasing rabbits!
so, did u solve your problem...
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so, did u solve your problem...
Umm, yes - it was a faulty alternator - and I replaced it completely. Old one went into the recycle.
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