Charging Malfunction...After Battery check and new alternator

[Frenchx3]

I got the "Charging Malfunction" warning indication the other day. Came home and measured the voltage at the battery while car was running and it read 11.4v. Went out the next morning and started the car and it read 14.5v so I knew the alternator was putting out again and the warning light disappeared. Started the drive to work and bam... "charging malfunction again". This time the car started to buck and skip a bit so I turned everything off and was able to make it back home without dying. Measured the voltage on the battery and it said 11.2 volts so I charged it up for a few hours and started the car and everything seemed fine again. While I was measuring the voltage at the battery with the car running it was 14.5 volts then the idle rpm dropped and so did the voltage...to 12.0v So I figured the alternator was cutting out.

Just to be sure I took the batter to a local parts store to have it checked. The analyzer said the battery was good but needed to be charged. So I ordered an alternator and put it in yesterday (and did the OFHG and the idler tensioner pulley while I was at it).

I started the car up and took it for a test drive and 1o minutes into the drive I get "CHARGING MALFUNCTION". I pulled over and disconnected the bus connector to the IBS on the negative cable and restarted the car. The light was out but came right back on again.

I'm at a loss for what the hell this could be..... Good battery, new alternator and still getting the charging malfunction error. Anyone have any ideas what I should check next??


2011 335 with N55 engine

[Pilgrim]

How about having a BMW-capable shop check it? There are limits to DIY testing.

[Codes2]

An alternator will stop outputting at a certain RPM, this doesn't dictate it's bad. BMW are better than most to output at 800 RPM... but I've observed this on multiple of mine.

It's possible there is a poor connection to the battery or elsewhere in the charging system.

The fact that the Charging Malfunction doesn't come on right away doesn't mean the issue isn't there on startup. It just takes a while to detect that the voltage is dropping, even though it is attempting to charge.

I've often run with a volt meter in my cigarette lighter, keeping an eye on voltage drop/spike patters. Not sure if you are also doing this.

Given that 'at the battery' you measure 14+ with the RPM up some does suggest that it's charging and that the voltage/current input to the batter is OK.
Gotta watch this value in transit to look for oddities.

Maybe there is even something in the car periodically polling excessive current, pulling the voltage down when it expects the levels to be rising based on the output to the battery.

Your car has been programmed for the battery that is in it, correct? (these cars to require the programming)

If you're doing everything right, and still seeing the warning and the battery is in-fact lowering in voltage after a drive - then I would suggest a competent mechanic/dealer. Whacked out battery issues have caused other issues ... the forum shows that... limit the potential issue spread.

[andrewwynn]

Make sure your engine ground is working. Measure voltage from chassis to the engine block. It should be millivolts.

If the voltage drop is more than 0.1v, then the ground straps are shot and will explain the problem your describe.

Also: measure voltage across the alternator directly.

B+ jump point under the hood to the engine block is the direct path to the alternator.

If the voltage at the alternator doesn't match the voltage at the battery the problem is cables.

If the B+ to block voltage is not stable it indicates a bad (regardless of age) alternator.

I suspect the vBat reported to OBD is chassis to bat so will not show alternator voltage.



Sent from my iPhone using Tapatalk Pro

[andrewwynn]

An alternator will stop outputting at a certain RPM, this doesn't dictate it's bad.

That is incorrect. At any RPM from idle to redline a properly functioning alternator will output a very stable output voltage. A dip in voltage below about 13.5 or even 14.0v indicates a distinct problem of an alternator not doing its only job.

"You only have one job" (produce current at a stable voltage)

[Codes2]

That is incorrect. At any RPM from idle to redline a properly functioning alternator will output a very stable output voltage. A dip in voltage below about 13.5 or even 14.0v indicates a distinct problem of an alternator not doing its only job.

"You only have one job" (produce current at a stable voltage)

I agree... in theory.
My 10 cars have shown that some, at very low idle will drop the current.
You can see the voltage dip, the lights dim, the fan slow.
Perhaps they were idling too low... however my wife's Toyota Matrix always does this at idle.

[Frenchx3]

Thanks for the replies. I have since taken the car to a local reputable BMW Indy. They had the car all day on Friday and spent several hours trying to diagnose my problem. They're telling me that there are multiple errors on the BSD line and that there are 4 components on that line: The alternator, oil level sensor, water pump and Intelligent Battery Sensor. They attempted to isolate the problem by disconnecting first the IBS Problem still there, then the oil level sensor and problem was still there. They can't disconnect the water pump but the watched the RPM of the pump while it was running and didn't notice any change that would indicate an issue. They deduced, based on these findings, that the problem must be with the alternator and that I should put in a new OEM or BMW alternator for $1250.

I'm not buying their diagnosis as the symptoms with the original factory alternator were the same as with new aftermarket alternator I just installed. I've also noticed a couple of other strange things since picking the car up from the Indy. I've been pulling codes using the Carly for BMW App and BT dongle and it is seeing faults:

Faultcode: (0x378F) BSD, communication (engine coolant pump): missing
Faultset 1:
(appeared at: 198384.0km)
battery voltage:
48.13 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
-25.50 °C
Water pump speed:
0.00 -
Faultcode: (0x378F) BSD, communication (engine coolant pump): missing
Faultset 2:
(appeared at: 2040.0km)
battery voltage:
57.34 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
48.75 °C
Water pump speed:
96.00 -
Faultcode: (0x378F) BSD, communication (engine coolant pump): missing
Faultset 3:
(appeared at: 288.0km)
battery voltage:
65.28 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
94.50 °C
Water pump speed:
0.00 -
Faultcode: (0x378F) BSD, communication (engine coolant pump): missing
Faultset 4:
(appeared at: 1016.0km)
battery voltage:
9.22 V
number of revolutions:
6144.00 rpm
Kuehlmitteltemperatur OBD:
120.00 °C
Water pump speed:
0.00 -
Faultcode: (0x378F) BSD, communication (engine coolant pump): missing
Faultset 5:
(appeared at: 1520.0km)
battery voltage:
32.51 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
143.25 °C
Water pump speed:
0.00 -


Faultcode: (0x38A4) Advanced communication Intelligent Battery Sensor: Malfunction
Faultset 1:
(appeared at: 198384.0km)
battery voltage:
65.28 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur Kuehlerausgang raw value:
0.59 V
Voltage Kl.87 raw value:
28.80 V
Faultcode: (0x38A4) Advanced communication Intelligent Battery Sensor: Malfunction
Faultset 2:
(appeared at: 524280.0km)
battery voltage:
57.34 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur Kuehlerausgang raw value:
2.52 V
Voltage Kl.87 raw value:
10.84 V
Faultcode: (0x38A4) Advanced communication Intelligent Battery Sensor: Malfunction
Faultset 3:
(appeared at: 288.0km)
battery voltage:
65.28 V
number of revolutions:
16320.00 rpm
Kuehlmitteltemperatur Kuehlerausgang raw value:
4.98 V
Voltage Kl.87 raw value:
28.80 V
Faultcode: (0x38A4) Advanced communication Intelligent Battery Sensor: Malfunction
Faultset 4:
(appeared at: 1016.0km)
battery voltage:
9.22 V
number of revolutions:
6144.00 rpm
Kuehlmitteltemperatur Kuehlerausgang raw value:
4.38 V
Voltage Kl.87 raw value:
0.00 V
Faultcode: (0x38A4) Advanced communication Intelligent Battery Sensor: Malfunction
Faultset 5:
(appeared at: 524280.0km)
battery voltage:
32.51 V
number of revolutions:
16320.00 rpm
Kuehlmitteltemperatur Kuehlerausgang raw value:
4.98 V
Voltage Kl.87 raw value:
0.00 V

Faultcode: (0x3792) Engine Cooling: Coolant pump speed is outside the tolerance
Faultset 1:
(appeared at: 198400.0km)
battery voltage:
49.66 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
-9.75 °C
Water pump speed:
0.00 -
Faultcode: (0x3792) Engine Cooling: Coolant pump speed is outside the tolerance
Faultset 2:
(appeared at: 1208.0km)
battery voltage:
57.34 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
48.75 °C
Water pump speed:
96.00 -
Faultcode: (0x3792) Engine Cooling: Coolant pump speed is outside the tolerance
Faultset 3:
(appeared at: 408.0km)
battery voltage:
38.66 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
97.50 °C
Water pump speed:
0.00 -
Faultcode: (0x3792) Engine Cooling: Coolant pump speed is outside the tolerance
Faultset 4:
(appeared at: 1032.0km)
battery voltage:
13.06 V
number of revolutions:
6144.00 rpm
Kuehlmitteltemperatur OBD:
120.00 °C
Water pump speed:
0.00 -
Faultcode: (0x3792) Engine Cooling: Coolant pump speed is outside the tolerance
Faultset 5:
(appeared at: 1552.0km)
battery voltage:
33.02 V
number of revolutions:
0.00 rpm
Kuehlmitteltemperatur OBD:
65.25 °C
Water pump speed:
0.00 -

These faults come and go but are generally always issues with the BSD Bus.

Another issue was the car went into limp mode driving home last night and reported "Engine Malfunction". Pulling over and restarting the engine cleared the limp mode and the voltage went back up to 14.6 volts on the display.

This afternoon while testing in the driveway I turned the engine off and removed the key and noticed that the water pump was running fully tilt for no apparent reason. Restarting then stopping the car immediately stopped the pump.

This thing has an angry gremlin in it. I'm hesitant to keep throwing parts at this thing as it's going to get expensive very quickly. I have another Indy I could take it to but I fear they'll run into the same issues as the first and just want to replace parts until it goes away.

Andrewwynn, I will try your suggestions and see what I find. Anyone else have any thoughts on what to try next?

[andrewwynn]

In your fault codes it shows a bunch of battery voltages that are way way too high. Even if those are just millisecond pulses that's enough to kill almost any electronic device.

It feels like defective voltage regulator to me.