radio volume cuts out a few seconds when I hit accelerator.

[scubajim20]

Trying to keep this short but a few things occurred. I was having an issue which I suspected was just the MID but I couldn't adjust the clock. It would start to adjust but then jump to another time. Also, after driving a bit the volume would cut out for a few seconds, but the display was visible/normal. Found a used MID and the clock is fine now but the volume issue still occurs.

I also noticed the lights on the dashboard will brighten as I hit the accelerator and dim a bit as it goes back to idle. I have an inexpensive battery/alternator tester and it showed an overvoltage error when performing the alternator test. (15.4v) I purchased a cheap digital voltmeter I plug into the cigarette lighter slot (it arrived last night)

While the car is running and if I turn on various lights and fans the meter is all over the place not sure how much swing is normal. I plan on monitoring it as I drive to work today. I'm suspecting it's the regulator in the alternator Again this is my third in the last three years. I am using remanufactured Bosch units. Any advice or diagnostic tips would be appreciated.

[BMW540san]

Hasn't someone mentioned here recently problem with remanufactured Bosch alternators which are basicaly Bosch by name only and Bosch has outsourced the job to crappy third party manufacturer.
Also, I believe it was also mentioned that Valeo is the best option at the moment?

[JimLev]

15.4v is too high. It should only fluctuate maybe 1 volt or so depending on what heavy current draw items you switch on.
In normal driving mine is reading 13.6v +/- 0.1volts

Your radio cutting out could be the amp. DSP or non-DSP?

[scubajim20]

I have DSP. On the drive today it was sitting at 14.1 +/- .1 radio and fan were on. When I was coming to a stop and putting the blinker on it would drop down to 12.5v and then 13.6 at idle and then back to 14v at cruising speed. Funny but the radio didn't act up on the short drive to work. Ill see how it is this evening and try to take longer ride.

[crdiscoverer]

Use the OBC to measure volts. Don't use cheap chinese chargers or you may get wrong values. It's normal that there's some brightness increase/decrease as you accelerate/idle, but it should be almost unnoticeable. 13.6 volts as measured by the OBC here too.

Here's something about the radio/MID. Few people know that E39s adjust volume depending on how fast you're going, this is to account for road noise and it's actually a setting you can adjust if you unlock the MID. Perhaps both the old and new MIDs are not getting the correct speed value from the other modules and they glitch out by cutting out sound? Unlock the MID and change that setting. It's worth a shot.

https://www.bimmerforums.com/forum/s...1#post12740911

[scubajim20]

Hasn't someone mentioned here recently problem with remanufactured Bosch alternators which are basicaly Bosch by name only and Bosch has outsourced the job to crappy third party manufacturer.
Also, I believe it was also mentioned that Valeo is the best option at the moment?

I could only find Valeo units that are not the water-cooled version. Best units still appear to be Bosch (reman.) or genuine BMW at over $1000.

[scubajim20]

Running around for a few days with the OBC set to #9 seems mostly normal. Two things randomly occur. 1st the car will some times drop to 12.2v for a moment when I come to a stop, then back to 13.8 +/-. Occasionally it will jump to 15.6v when I accelerate. I am guessing that's a large sweep so I am thinking the regulator or a bad ground. I need to do a detailed look at the grounds to remove and clean them. If no improvement I think I will replace the alternator and drop in a new battery, unless there is another module that might be part of the issue. This is where my knowledge base ends.

[JimLev]

Dropping to 12.2 for a moment is pretty normal, especially if you have other things on. I can’t ever remember mine reading more than 13.8/13.9 volts.
Remove the ground strap from the pass side engine mount to the bottom of the frame rail, that will most likely have the most corrosion on it.
I was surprised mine had some corrosion on it as I never drove it in the winter when when I lived in MA.

[scubajim20]

I understand this is getting tedious, I do appreciate the guidance.

[scubajim20]

I hate to go to a thread and find a lack of conclusion or follow up so here is where I stand. I think part of my electrical issue was a failing Aux fan. I was out a month ago, hot day, ac on, parked at Lowes and I got a temperature warning message. I opened the hood to check for leaks but noticed the Aux fan was not running. Drove home and parked it. I found that fuse 75 (50 amp behind glove compartment was shot) replaced it but it blew again. Through a few videos it seemed to simply be the fan. I replaced it last weekend (looked like the original) and also pulled off every ground I could locate and cleaned them (all seemed fairly typical looking).

Everything seems to be running normal. No radio cut out and watching the voltage on the dash every day it seems to have a typical fluctuation. I do to get a spike of 14.4 on a quick random acceleration.

[ross1]

I hate to go to a thread and find a lack of conclusion or follow up so here is where I stand. I think part of my electrical issue was a failing Aux fan. I was out a month ago, hot day, ac on, parked at Lowes and I got a temperature warning message. I opened the hood to check for leaks but noticed the Aux fan was not running. Drove home and parked it. I found that fuse 75 (50 amp behind glove compartment was shot) replaced it but it blew again. Through a few videos it seemed to simply be the fan. I replaced it last weekend (looked like the original) and also pulled off every ground I could locate and cleaned them (all seemed fairly typical looking).

Everything seems to be running normal. No radio cut out and watching the voltage on the dash every day it seems to have a typical fluctuation. I do to get a spike of 14.4 on a quick random acceleration.

Sounds like you got it, fingers crossed for you. It's amazing what a wonky ground can do, especially when one device then decides to take it's path to ground through another device.