Alternator or Idle control valve failing?

bmwpower603 · 03-02-2020, 07:52 PM

I knew that I was going to have to replace my ICV, or alternator sooner than later.

Car ran fine, until I got home and let it idle for a bit. It still runs fine tbh. But the idle dipped a several times, and saw the voltage also dip to like 13.6. I couldn’t catch the real bad idle dip on video. But this is what it looks like.

I’ll put ISTA on it tomorrow. But highly doubt there’s any codes. I have been getting a shadow code related to instrument cluster voltage. I’ll see if that is still appearing.

Here’s a video

https://m.youtube.com/watch?feature=...&v=3qZZn3bTSYc

Here’s the fault codes. (Might be unrelated)
Maybe it’s a voltage regulator. Does anyone know where it’s located on this vehicle? Mounted directly on the alternator ?

bmwpower603 · 03-03-2020, 07:18 AM

I want to also add. That I had just put gas in it. I didn’t fill it up all the way. Just half way.

I did notice my gas cap also looks aftermarket. I’ll continue to drive it and see if I can replicate.

Kwike92M3 · 03-05-2020, 11:23 AM

Honestly, it looks as if the alternator voltage regulator has failed. Cars operate off a 12v system, and typically charge around the 13.7-14.2 volt mark. Im not extremely well versed in BMW electronics, but > 16 volts is way too high. I would start by measuring the voltage @ the alternator and at the battery while the vehicle is running. At idle, it should be somewhere around 13.7-14.2 with loads off, but higher if other loads are on, depending on "desired output" from the DME. While the ignition is off, the battery should read 12.6v ( maybe 12.4-12.5v depending on battery age, condition, etc).

If battery voltage is above 16volts while at idle, shut the car off immediately. Too high of voltage can very easily damage multiple computers if exposed too long. I had a tahoe at one of my shops burn through a PCM, ABS Module, and TCS due to a customer ignoring all of the symptoms and continue to drive the car.
Keep in mind it is VERY possible that the voltage regulator is intermittently failing, and is not acting up all of the time.

Erratic voltage (in any car) can cause some super wonky symptoms. Address the voltage issue first, then look into the other problems, if any. Also, its a good idea to have the battery checked with a tester to make sure it is in good order.

bmwpower603 · 03-05-2020, 06:35 PM

Sounds like I should throw an alternator at it.

I’m bringing it to 3D Autoworks on Monday. I need to have the entire car checked out anyways.

03-02-2020, 07:52 PM	#1
bmwpower603 Lieutenant 204 Rep 486 Posts Drives: E36 m3 coupe 08 e90 M3 Join Date: Oct 2018 Location: New Hampshire iTrader: (0)	Alternator or Idle control valve failing? I knew that I was going to have to replace my ICV, or alternator sooner than later. Car ran fine, until I got home and let it idle for a bit. It still runs fine tbh. But the idle dipped a several times, and saw the voltage also dip to like 13.6. I couldn’t catch the real bad idle dip on video. But this is what it looks like. I’ll put ISTA on it tomorrow. But highly doubt there’s any codes. I have been getting a shadow code related to instrument cluster voltage. I’ll see if that is still appearing. Here’s a video https://m.youtube.com/watch?feature=...&v=3qZZn3bTSYc Here’s the fault codes. (Might be unrelated) Maybe it’s a voltage regulator. Does anyone know where it’s located on this vehicle? Mounted directly on the alternator ? Last edited by bmwpower603; 03-02-2020 at 07:57 PM..
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03-03-2020, 07:18 AM	#2
bmwpower603 Lieutenant 204 Rep 486 Posts Drives: E36 m3 coupe 08 e90 M3 Join Date: Oct 2018 Location: New Hampshire iTrader: (0)	I want to also add. That I had just put gas in it. I didn’t fill it up all the way. Just half way. I did notice my gas cap also looks aftermarket. I’ll continue to drive it and see if I can replicate. Last edited by bmwpower603; 03-03-2020 at 08:32 AM..
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03-05-2020, 11:23 AM	#3
Kwike92M3 Private First Class 74 Rep 146 Posts Drives: 2011 E92 M3 Supercharged Join Date: Aug 2014 Location: Dallas iTrader: (2)	Honestly, it looks as if the alternator voltage regulator has failed. Cars operate off a 12v system, and typically charge around the 13.7-14.2 volt mark. Im not extremely well versed in BMW electronics, but > 16 volts is way too high. I would start by measuring the voltage @ the alternator and at the battery while the vehicle is running. At idle, it should be somewhere around 13.7-14.2 with loads off, but higher if other loads are on, depending on "desired output" from the DME. While the ignition is off, the battery should read 12.6v ( maybe 12.4-12.5v depending on battery age, condition, etc). If battery voltage is above 16volts while at idle, shut the car off immediately. Too high of voltage can very easily damage multiple computers if exposed too long. I had a tahoe at one of my shops burn through a PCM, ABS Module, and TCS due to a customer ignoring all of the symptoms and continue to drive the car. Keep in mind it is VERY possible that the voltage regulator is intermittently failing, and is not acting up all of the time. Erratic voltage (in any car) can cause some super wonky symptoms. Address the voltage issue first, then look into the other problems, if any. Also, its a good idea to have the battery checked with a tester to make sure it is in good order.
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03-05-2020, 06:35 PM	#4
bmwpower603 Lieutenant 204 Rep 486 Posts Drives: E36 m3 coupe 08 e90 M3 Join Date: Oct 2018 Location: New Hampshire iTrader: (0)	Sounds like I should throw an alternator at it. I’m bringing it to 3D Autoworks on Monday. I need to have the entire car checked out anyways.
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