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      04-23-2015, 08:44 AM   #1
Farroar
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Voltage Regulator? Battery? Alternator? How To/Diagnosis

Hey folks,

I've been searching for info on how to properly diagnose the source of a battery related issue and I've found a lot of info here an there but not much about how to differentiate between the above topics. The Bentley manual doesn't give much info on these items really.

I have been having an issue with my car that has been pretty benign until recently. Really cold day a couple months back I couldn't start my car. It was like -20F. Had it jumped and didn't think much of it. Was sitting in my car having lunch and listening to the radio with engine off... car wouldn't start. Had to get it jumped again. That was a month ago. Now, the car won't start without a booster. All lights power up fine and the little battery icon doesn't even pop up on the display. Just won't start.

So this got me to thinking as the battery isn't that old.

How do I differentiate between alternator, battery, and power regulator?

What are the best ways to test each for correct functionality?

I have the INPA software and can mess with that a bit but wanted to see if I could get some parameters that I need to check.

I did check voltage at the battery when the car was on and off and it seemed to be off of what was listed in the Bentley. That is said to point to a regulator issue but I'm not convinced. So, before I go nuts on replacing parts I'd like to see if there is a good breakdown for each component. Could be a combination I suppose.

Thanks!
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      04-23-2015, 09:12 AM   #2
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Quote:
Originally Posted by Farroar View Post
Hey folks,

I've been searching for info on how to properly diagnose the source of a battery related issue and I've found a lot of info here an there but not much about how to differentiate between the above topics. The Bentley manual doesn't give much info on these items really.

I have been having an issue with my car that has been pretty benign until recently. Really cold day a couple months back I couldn't start my car. It was like -20F. Had it jumped and didn't think much of it. Was sitting in my car having lunch and listening to the radio with engine off... car wouldn't start. Had to get it jumped again. That was a month ago. Now, the car won't start without a booster. All lights power up fine and the little battery icon doesn't even pop up on the display. Just won't start.

So this got me to thinking as the battery isn't that old.

How do I differentiate between alternator, battery, and power regulator?

What are the best ways to test each for correct functionality?

I have the INPA software and can mess with that a bit but wanted to see if I could get some parameters that I need to check.

I did check voltage at the battery when the car was on and off and it seemed to be off of what was listed in the Bentley. That is said to point to a regulator issue but I'm not convinced. So, before I go nuts on replacing parts I'd like to see if there is a good breakdown for each component. Could be a combination I suppose.

Thanks!

Sounds like a dead battery. I would throw a battery charger on it overnight. If you have a situation where you can't start it again I would say battery.

You can throw a multi meter on it while running. You should be seeing around 14 volts. If you're seeing 14 volts Your alternator and voltage regulator are fine (voltage regulators are usually built into the alternator, not sure how the IBS works on this car though).

These cars take a lot of voltage and need to have a charger thrown on them once every few months, especially in cold weather.
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      04-23-2015, 09:34 AM   #3
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Thanks for the info. So, testing at the battery while running is measuring the voltage that the alternator is putting out? If I were to test the same location while the car is not running, that would show me the output from the battery I'd assume.

If the car is revving to say 2K while testing at the battery, I assume that the 14 volts should maintain? If it does fluctuate does this point to an issue with the alternator?

Lastly, what's IBS?

Thanks!
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      04-26-2015, 06:38 PM   #4
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Originally Posted by Farroar View Post
Lastly, what's IBS?

Thanks!
IBS = Intelligent Battery Sensor. It is contained in the negative cable, monitors the battery and essentially informs the alternator of the proper charging rate.

When mine developed an intermittent fault, all sorts of electrical weirdness followed - so you may wish to have it tested by a competent BMW mechanic.

Tom
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      04-26-2015, 08:18 PM   #5
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Testing from Alternator is ideal but its hard to get to. If you test from the battery you'll be measuring the voltage that the IBS is letting go to the battery. So if there's something wrong with the IBS you might think its the alternator. But if you test at the battery and you get 14 ish volts your alternator and IBS are probably OK and you need a bettery or a charge.
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      04-26-2015, 08:19 PM   #6
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Also yes you can test voltage directly at the battery or under the hood at the jump terminals on the passenger side
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      08-07-2015, 03:15 PM   #7
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IBS Issue?

Hi OP, Just wondering if you figured out the solution to your post. I have e90 330d 2005, with similar issues. I am getting 14v, had the alternator and battery tested and both are fine. But every 6 or so start ups I get a bunch of error lights - battery, abs, run flats, red cog and limp mode. A restart clears the lights but error still stored. The source of the issue appears to be with the IBS as that is the only fault that remains or reappears when everything else is cleared. The battery does not have IBS fitted at all, and has never had IBS. The error code is "4a27 - Intelligent battery sensor - communication". Did you come across this at all? Any ideas anyone? Thanks
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      10-29-2019, 11:57 AM   #8
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Any updates I got a battery charging warning on my 335is after working on it with Fmic and intakes now my cars going crazy dies within minutes after a jump I want to see maybe I shorted something or what's going on Ik it's something with alternator because my battery is good but idk if it wires I shorted from the intakes touching alternator or what
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      10-29-2019, 07:33 PM   #9
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If my memory serves right, both the alternator cable and the voltage regulator plug from the alternator are under the stock airbox. So, working on that could have nicked or knocked lose a plug or cable, maybe. Also, in the N54 and N52 engines the voltage regulator, a $45 part, can be changed w/o removing the entire alternator. If I remember correctly, running the car with all the accessories off should produce a fairly consistent 14 volts at the battery, if that is not the case, it is indicative of a voltage regulator issue.
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      08-19-2022, 09:04 PM   #10
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Quote:
Originally Posted by Nikon User View Post
Hi OP, Just wondering if you figured out the solution to your post. I have e90 330d 2005, with similar issues. I am getting 14v, had the alternator and battery tested and both are fine. But every 6 or so start ups I get a bunch of error lights - battery, abs, run flats, red cog and limp mode. A restart clears the lights but error still stored. The source of the issue appears to be with the IBS as that is the only fault that remains or reappears when everything else is cleared. The battery does not have IBS fitted at all, and has never had IBS. The error code is "4a27 - Intelligent battery sensor - communication". Did you come across this at all? Any ideas anyone? Thanks
bmw fault 4A27: Intelligent Battery Sensor (IBS), missing. For anyone in the future...

for me this fault will not go away. ive replaced the ibs cable. main symptoms for me are crank, no start. from what i can find on the forums, bad ibs causes a no start
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