Charging System Troubleshooting

RobertoTaylor · 11-27-2015, 08:53 AM

I need some troubleshooting help guys!

Two weeks ago my car had some electrical issues and went to the shop right before I left for Baja. At the shop, it was determined that it was the alternator that was at fault, and it got replaced. Well, I picked up my car on Wednesday, and everything seemed fine. Yesterday on my way over to my gf's house for Thanksgiving, I was sitting at a stop light when I got the engine malfunction screen. I immediately looked at the voltage on my ScanGauge, and it was reading 9.7V, which is the same voltage it was at before when it gave me the error messages and went into limp mode last time. Once the voltage drops to 9.5V, it gives me a transmission malfunction screen, and the tranny feels like it slips.

The weird thing about this is that when the voltage drops that low, it only stays like that for maybe 10 seconds, then it jumps back up to around 13.6V. I can then shut the car off, start it back up, and everything is back to normal. This morning on my way to work it happened again. I kept an eye on my voltage this time when I left the house, and it starts to slowly drop from 13.6V down. This morning it actually dropped all the way down to 9.0V before jumping back up to mid 13's.

It's going to probably go back to the shop today to get checked, and one of my brothers thoughts is that it could be a bad cell in the battery. Although I told him it doesn't make much sense to me since it's the alternator that runs keeps the electrical system going while the car is running, and not the battery, but I could be wrong.

Has anyone heard of or experienced this type of issue before that could give me a couple of pointers? Any help will be greatly appreciated.

UPDATE:

This all had to do with a bad water pump. Since the alternator, water pump, and IBS are all tied together, things tend to act wacky when one of them goes bad.

Wilt · 11-27-2015, 11:06 AM

Maybe a cell in the battery is getting to where it shorts out for a bit, instantly decreasing the voltage of the battery from 12V+ to 10V?!

But you are right, the alternator and voltage regulator should be what is read during charging, yet you need to keep in mind that it is NOT ALWAYS 'charging'...the IBS reads the battery voltage periodically and tells the DME what voltage to have supplied, so maybe a bad cell causes the IBS to go whacky and not request output from the VR.

RobertoTaylor · 11-27-2015, 11:23 AM

Quote:

Originally Posted by Wilt

Maybe a cell in the battery is getting to where it shorts out for a bit, instantly decreasing the voltage of the battery from 12V+ to 10V?!

But you are right, the alternator and voltage regulator should be what is read during charging, yet you need to keep in mind that it is NOT ALWAYS 'charging'...the IBS reads the battery voltage periodically and tells the DME what voltage to have supplied, so maybe a bad cell causes the IBS to go whacky and not request output from the VR.

Thanks for the info. The other thing I've been reading is about AGM vs non-AGM batteries. The battery on my car was replaced before I purchased it, but I don't know if it came with an AGM or non-AGM battery. I believe what's in there now is non-AGM, so from what I've been reading the car needs to be coded to know it's an non-AGM battery, otherwise it will affect the way the battery is charged.

How would I know if my car came with an AGM battery or not from the factory?

ctuna · 11-27-2015, 02:39 PM

You need to find out what its coded for now.
Most of these cars came with a Lead Acid battery of
around 90ah capacity. I would put a full charge on the battery
and check its health as a starting point.
You need a coding setup or some means to read what its
set up for now.
I would take it back to the people that were suppose to have fixed it.
Did you have the power cable recall to the cabin fuse box recall done?

Wires · 11-27-2015, 06:03 PM

+1 on the battery. Typically what happens is either the battery or alternator fails, destroying the other one.

If you change the battery, it should be fine. If you continue to run it, it will destroy the regulator in the alternator. (vicious cycle of pain.

)

RobertoTaylor · 11-27-2015, 06:58 PM

Okay guys, put on your thinking caps because this is just too weird. While on my way to shop, voltage dropped all the way down to 8V while driving 70mph on the freeway. After a few seconds it jumps back up to about 13.5V. Drove the car the rest of the way to the shop in limp mode.

Once at the shop, we hook up the multimeter to the battery with the car off. Reads 12V steady. Hook up the battery tester, and it passes. Start the car, and it dips to 11.2V, but then jumps back up to 13.5V after a few high revs. Drove it for about 5 miles to see if it would drop, and it didn't. Get back to the shop, shut it off, turn it back on, and it's not charging again. Now this is getting weird. After a couple of high revs (has to be over 5K) it starts charging again. So it seems that for some reason the alternator won't start charging unless I rev it past 5K RPM.

The battery is maybe 6 months old, and the alternator was just replaced last week.

ctuna · 11-27-2015, 07:49 PM

So when did the symtoms start ?
If it was after the alternator was installed maybe
they gave you a bad one or installed it wrong .
The charging system on these is complicated.
Hows the ground strap to the Engine?

http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja

RobertoTaylor · 11-27-2015, 09:28 PM

Quote:

Originally Posted by ctuna

So when did the symtoms start ?
If it was after the alternator was installed maybe
they gave you a bad one or installed it wrong .
The charging system on these is complicated.
Hows the ground strap to the Engine?

http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja

Symptoms started a few weeks ago which is why I had the alternator replaced. It could be a bad new alternator, so we'll see. I'll check the ground strap in the morning.

Tom K. · 11-27-2015, 10:59 PM

After two alternators were replaced in my E91, the problem was finally found to be an intermittently bad IBS.

Tom

RobertoTaylor · 11-28-2015, 04:44 PM

Quote:

Originally Posted by Tom K.

After two alternators were replaced in my E91, the problem was finally found to be an intermittently bad IBS.

Tom

Is there a way to troubleshoot the IBS to see if that's the problem?

ctuna · 11-28-2015, 08:15 PM

I believe you can pull the power to it and the car runs
off default values.

RobertoTaylor · 11-29-2015, 10:44 PM

One last question, does anyone know if the stock e90 335i came with an AGM battery or not? I'm thinking that may be the problem, but is there a way to find out?

robthewrench · 11-30-2015, 10:37 AM

Not all 335's came with AGM. It was an option.

RobertoTaylor · 11-30-2015, 10:57 PM

My car is pretty much fully loaded. Sport pkg, Premium pkg, nav, etc.

Would the dealer be able to tell me for sure if it came with one or not?

808AWD325xi · 12-05-2015, 08:59 PM

Quote:

Originally Posted by RobertoTaylor

One last question, does anyone know if the stock e90 335i came with an AGM battery or not? I'm thinking that may be the problem, but is there a way to find out?

Generally speaking, most came with lead acid batteries. White OEM batteries are lead acid, black for AGM.

To know definitively which type of battery the car is coded for, read the CAS module with NCS-Expert. Lead acid batteries won't have the _agm suffix.

RobertoTaylor · 12-07-2015, 09:38 PM

So it was determined that the new alternator was bad, and we ordered a new one. New alternator was installed today, but when we went to start the car, the battery was completely dead.

Jump started the car, and the alternator is now making a really strange whining sound, and when I turn the car off the water pump will not turn off which is causing the drain on the battery.

Water pump and alternator are both new less than a month old. Anyone have any ideas as to why it would just keep running?

ctuna · 12-08-2015, 11:47 PM

where are you or these guys getting part?

lookalikehuuh · 12-09-2015, 03:33 AM

Sounds like quite the shoddy parts you are getting there.

1st i would definitely suggest you get a QUALITY alternator. I was in your situation once and was forced to buy the alternator at Autozone since they were the only ones with one in stock. Even the dealer had to order one. Anyway... after half the car's sensors stopped working(oil sensor, would not idle), random power spikes (11v-16v) I said F this and had the original alternator rebuild by my local rebuilder. Opted for only the top quality brushes and bearings. Anyway once the original alternator went back in suddenly everything works perfect. Oil sensor was working, no more voltage spikes and idle was smooth as silk. The Alternator BUS appears to be directly tied to many of the car's systems which causes all kinds of weird issues if there is a problem with communication.

Anyway, get quality parts as these cars are very finicky to begin with no need to add fuel to the fire.

RobertoTaylor · 12-09-2015, 06:13 PM

Thanks for the tip guys. The thermostat and water pump are OEM. The alternator was an aftermarket Bosch.

11-27-2015, 08:53 AM	#1
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	Charging System Troubleshooting I need some troubleshooting help guys! Two weeks ago my car had some electrical issues and went to the shop right before I left for Baja. At the shop, it was determined that it was the alternator that was at fault, and it got replaced. Well, I picked up my car on Wednesday, and everything seemed fine. Yesterday on my way over to my gf's house for Thanksgiving, I was sitting at a stop light when I got the engine malfunction screen. I immediately looked at the voltage on my ScanGauge, and it was reading 9.7V, which is the same voltage it was at before when it gave me the error messages and went into limp mode last time. Once the voltage drops to 9.5V, it gives me a transmission malfunction screen, and the tranny feels like it slips. The weird thing about this is that when the voltage drops that low, it only stays like that for maybe 10 seconds, then it jumps back up to around 13.6V. I can then shut the car off, start it back up, and everything is back to normal. This morning on my way to work it happened again. I kept an eye on my voltage this time when I left the house, and it starts to slowly drop from 13.6V down. This morning it actually dropped all the way down to 9.0V before jumping back up to mid 13's. It's going to probably go back to the shop today to get checked, and one of my brothers thoughts is that it could be a bad cell in the battery. Although I told him it doesn't make much sense to me since it's the alternator that runs keeps the electrical system going while the car is running, and not the battery, but I could be wrong. Has anyone heard of or experienced this type of issue before that could give me a couple of pointers? Any help will be greatly appreciated. UPDATE: This all had to do with a bad water pump. Since the alternator, water pump, and IBS are all tied together, things tend to act wacky when one of them goes bad. Last edited by RobertoTaylor; 02-26-2016 at 01:36 PM..
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11-27-2015, 11:06 AM	#2
Wilt Major 228 Rep 1,045 Posts Drives: 2011 328i Join Date: Mar 2015 Location: SF Bay area iTrader: (0)	Maybe a cell in the battery is getting to where it shorts out for a bit, instantly decreasing the voltage of the battery from 12V+ to 10V?! But you are right, the alternator and voltage regulator should be what is read during charging, yet you need to keep in mind that it is NOT ALWAYS 'charging'...the IBS reads the battery voltage periodically and tells the DME what voltage to have supplied, so maybe a bad cell causes the IBS to go whacky and not request output from the VR.
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11-27-2015, 02:39 PM	#4
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	You need to find out what its coded for now. You need to find out what its coded for now. Most of these cars came with a Lead Acid battery of around 90ah capacity. I would put a full charge on the battery and check its health as a starting point. You need a coding setup or some means to read what its set up for now. I would take it back to the people that were suppose to have fixed it. Did you have the power cable recall to the cabin fuse box recall done?
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11-27-2015, 06:03 PM	#5
Wires Brigadier General 1646 Rep 4,877 Posts Drives: 2016 340i xDrive Join Date: Apr 2008 Location: Calgary iTrader: (0)	+1 on the battery. Typically what happens is either the battery or alternator fails, destroying the other one. If you change the battery, it should be fine. If you continue to run it, it will destroy the regulator in the alternator. (vicious cycle of pain. )
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11-27-2015, 06:58 PM	#6
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	Okay guys, put on your thinking caps because this is just too weird. While on my way to shop, voltage dropped all the way down to 8V while driving 70mph on the freeway. After a few seconds it jumps back up to about 13.5V. Drove the car the rest of the way to the shop in limp mode. Once at the shop, we hook up the multimeter to the battery with the car off. Reads 12V steady. Hook up the battery tester, and it passes. Start the car, and it dips to 11.2V, but then jumps back up to 13.5V after a few high revs. Drove it for about 5 miles to see if it would drop, and it didn't. Get back to the shop, shut it off, turn it back on, and it's not charging again. Now this is getting weird. After a couple of high revs (has to be over 5K) it starts charging again. So it seems that for some reason the alternator won't start charging unless I rev it past 5K RPM. The battery is maybe 6 months old, and the alternator was just replaced last week.
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11-27-2015, 07:49 PM	#7
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	So when did the symtoms start ? So when did the symtoms start ? If it was after the alternator was installed maybe they gave you a bad one or installed it wrong . The charging system on these is complicated. Hows the ground strap to the Engine? http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja
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11-27-2015, 10:59 PM	#9
Tom K. Major General 124 Rep 5,627 Posts Drives: '07 328iT, '13 Boxster Join Date: Mar 2008 Location: Maryland iTrader: (0)	After two alternators were replaced in my E91, the problem was finally found to be an intermittently bad IBS. Tom
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11-28-2015, 08:15 PM	#11
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	I believe you can pull the power to it I believe you can pull the power to it and the car runs off default values.
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11-29-2015, 10:44 PM	#12
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	One last question, does anyone know if the stock e90 335i came with an AGM battery or not? I'm thinking that may be the problem, but is there a way to find out?
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11-30-2015, 10:37 AM	#13
robthewrench Captain 266 Rep 952 Posts Drives: 11 E90 335i Join Date: Aug 2014 Location: Columbus OH iTrader: (0)	Not all 335's came with AGM. It was an option. __________________ bone stock
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11-30-2015, 10:57 PM	#14
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	My car is pretty much fully loaded. Sport pkg, Premium pkg, nav, etc. Would the dealer be able to tell me for sure if it came with one or not?
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12-07-2015, 09:38 PM	#16
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	So it was determined that the new alternator was bad, and we ordered a new one. New alternator was installed today, but when we went to start the car, the battery was completely dead. Jump started the car, and the alternator is now making a really strange whining sound, and when I turn the car off the water pump will not turn off which is causing the drain on the battery. Water pump and alternator are both new less than a month old. Anyone have any ideas as to why it would just keep running?
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12-08-2015, 11:47 PM	#17
ctuna Lieutenant General 1911 Rep 13,104 Posts Drives: 325xi 06 wagon MT Join Date: Jan 2010 Location: Santa Cruz, Ca iTrader: (0)	where are you or these guys getting part? where are you or these guys getting part?
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12-09-2015, 03:33 AM	#18
lookalikehuuh Major 700 Rep 1,227 Posts Drives: 2006 330i, 2007 335i Join Date: Sep 2014 Location: San Diego, CA iTrader: (0)	Sounds like quite the shoddy parts you are getting there. 1st i would definitely suggest you get a QUALITY alternator. I was in your situation once and was forced to buy the alternator at Autozone since they were the only ones with one in stock. Even the dealer had to order one. Anyway... after half the car's sensors stopped working(oil sensor, would not idle), random power spikes (11v-16v) I said F this and had the original alternator rebuild by my local rebuilder. Opted for only the top quality brushes and bearings. Anyway once the original alternator went back in suddenly everything works perfect. Oil sensor was working, no more voltage spikes and idle was smooth as silk. The Alternator BUS appears to be directly tied to many of the car's systems which causes all kinds of weird issues if there is a problem with communication. Anyway, get quality parts as these cars are very finicky to begin with no need to add fuel to the fire.
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12-09-2015, 06:13 PM	#19
RobertoTaylor Private First Class 44 Rep 105 Posts Drives: 2012 BMW 535i \| 2015 BMW X5 Join Date: Jul 2015 Location: Arizona iTrader: (0)	Thanks for the tip guys. The thermostat and water pump are OEM. The alternator was an aftermarket Bosch.
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