11.9 volts engine running says nothing from alternator to me!

So, rather than add to the fog of theories on this thread I will offer up some recent experience; vehicle '63 plate 4x4 TA 73k miles.

I replaced the battery maybe 18 moths ago, there was some sluggish starting and the Stop Start (SS) had stopped functioning maybe 6 months before this. There is much out there that points to poor battery performance resulting in the loss of SS, and I was always disconcerted when the car cut out when in traffic so loss of SS was never an issue.

More recently there were random messages relating to loss of SS, hill holder not available, ESC unavailable along with the yellow engine warning triangle. As the frequency and number of warnings increased I decided to get some "proper" diagnosis done and visited a well trusted Alfa specialist.

The almost instant diagnosis was the brake light switch (WTF??) and voltage controller that sits on the battery negative post. They fitted a new brake light switch (note for RHD cars this is on the passenger side) and while not having the voltage regulator "gave" me a second hand replacement off a MiTo that had expired.

The outcome; SS restored no more nonsense 4x4 ASC ESC Hillholder messages etc. All the above work plus oil and filters and diagnosis of Blue and Me controller failure £200 incl. all sorted in less than 3 hours; thank you very much Jamie!

Well I'm very glad your problem was fixed cheaply and you had good service.

The poster in Germany is interested in fixing his problem himself. Which is why he has asked for our technical help.

jackwhoo said:

Well I'm very glad your problem was fixed cheaply and you had good service.

The poster in Germany is interested in fixing his problem himself. Which is why he has asked for our technical help.

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Relax. like I said just offering my experience which in my view is what these forums are for; I see very little technical help here. Re read my post and I think there are similarities in the symptoms, I don't consider myself qualified to offer "technical solutions".

The results of a batterie test.

Thx for all the contributions.
Herts Hillhopper: Sounds reasonable. Will record metrics during "flight" to see, wether and when the voltage goes up. Might corroborate your theory which reads sound enough.

As I only have a pc with Multiecuscan to do the recording, do you have a suggestion as to which ECU to observe?

And just to confirm: You are putting forward the proposition, that the "static" batterie test done in the garage is not telling the whole story - just to say the least. Did I get your idea?

Thx,
David

BlackForest said:

Thx for all the contributions.

Herts Hillhopper: Sounds reasonable. Will record metrics during "flight" to see, wether and when the voltage goes up. Might corroborate your theory which reads sound enough.

As I only have a pc with Multiecuscan to do the recording, do you have a suggestion as to which ECU to observe?

And just to confirm: You are putting forward the proposition, that the "static" batterie test done in the garage is not telling the whole story - just to say the least. Did I get your idea?

Thx,
David

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Hi David
Yes, you have understood me correctly.
I have not used ECU scan (nor any other data reader) so cannot answer your second question.

Hello,

after looking at the attached diagram, it looks as if the alternator would be OK. It only loads the battery, when the car is decelerating, i.e. it uses the power of the engine to accelerate the vehicle and on deceleration it reuses the kinetic energy in the car to charge the battery.

The kind of static battery test the garagist made is not adequat.

Am I right? What are your thoughts?

Thx,
David

I really think there is a problem if voltage can drop to 11.9 volts with engine running. Which is when 4x4 turns off.

Even with a smart charge alternator I would think there is voltage set point at which alternator should not allow the system to drop below.

I am not sure the battery test result is conclusive that battery is good.

If battery fully charged off the car then refitted does the 4x4 still stop working and voltage drop to 11.9volts when 4x4 tries to work? If so battery could be faulty.
Worth looking into condition of battery sensor that is part of -ve connection at battery.

When replacing battery on car with smart charge alternator are you required to tell body control module new battery fitted ?

Lots of problems are caused by bad battery -ve wires and corroded connections of battery-ve wire.
Have you removed -ve wire and cleaned connections?

jackwhoo: Might be well worth a try! Perhaps I can do this tomorrow. Then I will be in the mountains. Will charge the battery and engage the hills!

The drop to 11.9V is indeed intriguing. What is the root cause of this? It is the time the solenoids (ABS, Traction Control, Diff-Control) are engaging, the ABS pump spins off. But all of these devices do work when I actuate them via MultiEcuScan. OK, all of the 8 ABS valves run through an not further specified error condition. Perhaps I should check the voltage with a multimeter while actuating! Chances are that I eventuall down spikes will escape me without an osci - to which I have no access :-(

I am sorry I cannot say for sure why the voltage drops so low.
Normally Voltage drops due to high current demand .
I see you have replaced your battery perhaps new battery is not able to provide the current demanded by edl 4x4 etc.

Please do check battery -ve wires and connections , resistance in wire or at connections will cause problems.

With engine running and all electrical things turned on lights, heated window , interior ventilation
- measure voltage at battery posts,
And voltage between alternator body and alternator +ve post.

Post result of measurements.

Voltage measurements with engine running at idle

jackwhoo said:

I don't know where to find wiring diagram.

Bernie may help.

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Who is Bernie, where to find him?

And is there something available like a description of which fuse is responsible for what and where it is located? Would already be helpful in identifying the points where to measure voltages...

Thx again for any help!
David

Using your multi meter measure volts at battery.

Using multi meter, put black meter lead on metal of engine then put red meter lead on big wire bolted to alternator, read volts.

BlackForest said:

jackwhoo: Might be well worth a try! Perhaps I can do this tomorrow. Then I will be in the mountains. Will charge the battery and engage the hills!

The drop to 11.9V is indeed intriguing. What is the root cause of this? It is the time the solenoids (ABS, Traction Control, Diff-Control) are engaging, the ABS pump spins off. But all of these devices do work when I actuate them via MultiEcuScan. OK, all of the 8 ABS valves run through an not further specified error condition. Perhaps I should check the voltage with a multimeter while actuating! Chances are that I eventuall down spikes will escape me without an osci - to which I have no access :-(

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Just an observation but at no point has anyone considered the power steering (PAS) as a source of the voltage drop while mobile. From rummaging under the dashboard the PAS certainly seems to have that potential given the diameter of the cables that connect it! Again, I don't have the knowledge to diagnose remotely but I would consider the function of the voltage regulator on the battery post.

The graph shows that the voltage didn’t drop below 12.6 volts during that journey, which I’d say shows that the alternator is working, and supplying a small amount of charge even when the engine is under load. Without reading back right through this thread, how old is the battery, and what mileage (total km) has the car recorded? How is it used - small, short journeys or long runs? Every day or less frequently? This might help answer if the battery is at fault.

Good idea to consider the intelligent battery sensor (IBS) on negative battery connector.
The IBS does have a lot to do with how the battery state of charge and battery health is calculated and so how the battery charging is managed.

This is where I was heading by suggesting fully charging battery off the car then seeing if fault still there.

Panda IIs said:

Just an observation but at no point has anyone considered the power steering (PAS) as a source of the voltage drop while mobile. From rummaging under the dashboard the PAS certainly seems to have that potential given the diameter of the cables that connect it! Again, I don't have the knowledge to diagnose remotely but I would consider the function of the voltage regulator on the battery post.

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so far as I know, the voltage sensor on the battery itself is only there for the stop/start system — and decides the battery has sufficient charge to restart the engine if it auto-stops.

Herts Hillhopper said:

The graph shows that the voltage didn’t drop below 12.6 volts during that journey, which I’d say shows that the alternator is working, and supplying a small amount of charge even when the engine is under load....

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Just coming in from running another test on the car. In the Body Control Unit I did observe the "Alternator Status" which knows the state "Noncharging" and "Recharging".

And as you thaught it really goes "Recharging" as soon as I start the engine, even when the car is idling.

Herts Hillhopper said:

... how old is the battery, and what mileage (total km) has the car recorded? How is it used - small, short journeys or long runs? Every day or less frequently?...

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- Did change the battery a few days ago. Same make, same model as the original one.
- Odometer is at about 167k km.
- Half city use (my wife) and short distances around hunting (me) and the other half is motorway > 100km per ride.

Thx to all for their thoughts!
David