E39 Randomly Loses 12v Power

[trevzor4242]

One more pic

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[trevzor4242]

Well it happened a ton this morning and I got video. Worse than it's ever been...
https://youtu.be/VDaoWB73VNk

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[Ed CT]

Well it happened a ton this morning and I got video. Worse than it's ever been...
https://youtu.be/VDaoWB73VNk

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So, at the last part of that vid, did your engine cut off when your tach went to zero?

[trevzor4242]

So, at the last part of that vid, did your engine cut off when your tach went to zero?

Yes when the video ended it stalled. I had no power for about 30 seconds so I had to deal with traffic. It eventually started about 30 seconds later.

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[JimLev]

Can you open the glove box and lower the fuses above the gb. Start the car and move the fuse assy up and down to see if it has any effect on loosing power.
Maybe drive it and have a helper wiggle the fuses too.

[Ed CT]

Yes when the video ended it stalled. I had no power for about 30 seconds so I had to deal with traffic. It eventually started about 30 seconds later.

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Absolutely no power? Or did you have stuff like cabin lights, parking lights, cig lighter power?

[trevzor4242]

Absolutely no power? Or did you have stuff like cabin lights, parking lights, cig lighter power?

It depends on the situation. Initially in the video there were times when it cut and uou could hear my music get quiet and lights on the dash flash. When that happened the amp lost power and the dash too but not everything, or it was too fast to affect some things like the radio and engine.

So I'm not sure for the first cases but in the end everything lost power for about 30 seconds.

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[JimLev]

Some of those fuse connections under the carpet look pretty crusty and a bit rusty.
I'd disconnect the battery and then one at a time remove the nuts and fuses to clean up the connections.
That may not be it but at least you've eliminated that as a potential problem.
As I think I said before all power for the cabin (and some stuff under the hood) goes thru those fuses. Same for the fuses above the glove box.

[jicaino]

I'll keep my suggestion of the ignition switch and add that you may want to unplug the VR (the thinner one of the 2 cables that runs under the valve cover beauty cover, that has a spring clip connector to the alternator) You may be having a failing VR that spikes when hot and lets the voltage go above 14.9 v since you don't have an EGS it would behave like that. Try accesing the hidden test #7 (or the 9? the one that shows the VBatt) when it's acting up

[trevzor4242]

I'll keep my suggestion of the ignition switch and add that you may want to unplug the VR (the thinner one of the 2 cables that runs under the valve cover beauty cover, that has a spring clip connector to the alternator) You may be having a failing VR that spikes when hot and lets the voltage go above 14.9 v since you don't have an EGS it would behave like that. Try accesing the hidden test #7 (or the 9? the one that shows the VBatt) when it's acting up

It's so hard to recreate and sporadic I'm not sure I could get it to happen while testing. I can see voltage from my radar detector though so I'll glance up at it next time it happens and check voltage.

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[trevzor4242]

Watching voltages a little on my drive home they hovered around 12.5-13.7V

Can you elaborate on why I should unplug part of the voltage regulator? I follow the logic of it being a potential issue but what would unplugging it do

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[jicaino]

I do not trust external devices as I don't know the resolution... try'n get an accurate IKE measure. Also if you take out the lock you can probably try'n squeeze some lube/contact cleaner past the mechanical part down on the ignition switch, although it has been discussed that very little if any gets pat the bottom of the mechanical lock part onto the switch itself.

[JimLev]

Unplugging the alt would stop it from charging. Without the battery charging a good battery would get drained in 30 min or less of driving.
Although with the voltage going high like jicaino mentioned shouldn't cause your instrument to crap out.

[trevzor4242]

Unplugging the alt would stop it from charging. Without the battery charging a good battery would get drained in 30 min or less of driving.
Although with the voltage going high like jicaino mentioned shouldn't cause your instrument to crap out.

Oh ok, so he was just suggesting I unplug the alternator from the VR?

I guess if the voltage got really high though the computer could maybe go into a fail safe mode and shut off? It's a long shot but just a thought.

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[trevzor4242]

Here's my current line of thinking... When this problem is at it's worst, the dash loses power along with the radio. I haven't confirmed anything else like the person asking about interior lights.

I'm going to follow the radios path. The radio is connected to a constant ground and positive lead along with a switched wire. In other words it always has power available, but turns on when the ignition sends it power in a separate wire.
The tiny instances of my issue don't always kill the radio but at it's worst this problem kicks everything off... In that instance, the radio loses all power, meaning the constant 12v source stops providing voltage or current. I know this because when it comes back on it prompts me about language selection. The ignition switch should have no effect on the constant power the radio sees, right? The radio gets constant power and turns on the moment the little turn on wire becomes active due to the ignition switch.

Basically what I'm saying is that the radio completely lost power, and that can't be due to the ignition switch because it's a constant source no matter if the car is on or off, right?

The last thing I want to do is dismiss a potential issue, but I have to think through and eliminate some things because otherwise I'll never narrow it down...

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[R Shaffner]

Forgive me for joining late and not reading all this thoroughly. Wouldn't an intermittent problem that affects many circuits point to a loose ground (which is where you were when you started this thread)?

That might be easy to test, if you can replace the ground for something that is being affected by the problem, or add a secondary ground for something that's not too hard to get to. Perhaps the radio or something that's not going through other control units. If the problem then goes away for that component, then you've found the problem.

[Leroy08]

I had something very similar happen when I first got my car. It was a dangerous situation as I was driving on an interstate during rush hour when the car lost electrical off and on very briefly - the dash lights went crazy, transmission went into failsafe and I almost had a semi rear end me. It turned out to be the battery. I don't know if a cell was intermittently shorting out or what, but the systems in these cars are pretty sensitive to voltage levels.

Is the battery condition known? How old is it?

[trevzor4242]

I had something very similar happen when I first got my car. It was a dangerous situation as I was driving on an interstate during rush hour when the car lost electrical off and on very briefly - the dash lights went crazy, transmission went into failsafe and I almost had a semi rear end me. It turned out to be the battery. I don't know if a cell was intermittently shorting out or what, but the systems in these cars are pretty sensitive to voltage levels.

Is the battery condition known? How old is it?

It's an AGM battery and I'm trying to find the date but it performs really well. Passes my load tester with flying colors and feels like it could crank all day. As aforementioned it sits around 12.5-13.5v

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[trevzor4242]

Progress? Maybe

Found frayed ground wires on the other side of the engine bay near the intake. I got the car with a dinan intake which sounds amazing, but I believe it rubbed these wires raw. Anyways, not sure this is responsible for the issues I've had but I hope so. Anyways this intake is a pain and I'll be tracing these broken wires a bit and replacing the broken sections asap.

Update: I pulled off the tape and found the damage to be localized at the wire's turn and rubbing point with the intake. That's good cause the other side melted and I think in this case friction just rubbed off insulation in the small area. Down side is I removed the ground terminal on the body there and everything powered on like normal, so even when those wires have no ground it seems to make no difference.



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[Ed CT]

Progress? Maybe

Found frayed ground wires on the other side of the engine bay near the intake. I got the car with a dinan intake which sounds amazing, but I believe it rubbed these wires raw. Anyways, not sure this is responsible for the issues I've had but I hope so. Anyways this intake is a pain and I'll be tracing these broken wires a bit and replacing the broken sections asap.

Update: I pulled off the tape and found the damage to be localized at the wire's turn and rubbing point with the intake. That's good cause the other side melted and I think in this case friction just rubbed off insulation in the small area. Down side is I removed the ground terminal on the body there and everything powered on like normal, so even when those wires have no ground it seems to make no difference.



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What about a short? Any of those frayed/exposed wires in proximity to a non-ground connection?

Also, in checking the battery connections, have you also checked the positive safety 'blasting cap' connection next to the positive battery terminal? Not the positive bat terminal to the positive cable nut connector, but the secondary connection to the explosive device. I've read in two other threads that this was their issue when they randomly lost electrical power.

And, Leroy08's suggestion of a battery cell intermittently failing is a possibility, too. If the battery's over 5 y.o. replacing it now would be a good PM measure.

[trevzor4242]

What about a short? Any of those frayed/exposed wires in proximity to a non-ground connection?

Also, in checking the battery connections, have you also checked the positive safety 'blasting cap' connection next to the positive battery terminal? Not the positive bat terminal to the positive cable nut connector, but the secondary connection to the explosive device. I've read in two other threads that this was their issue when they randomly lost electrical power.

And, Leroy08's suggestion of a battery cell intermittently failing is a possibility, too. If the battery's over 5 y.o. replacing it now would be a good PM measure.

Yes they are in proximity to positive wires but I'd be surprised if that hasn't blown a fuse by now if it shorted.
I just patched the wire's together and I doubt it will make any difference but I'm glad it's fixed and it's one less possibility.

I haven't checked the blasting cap, i don't even know about that but it sounds kind of extreme lol. Will check it

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[jicaino]

Yeah I was suggesting unplugging the VR and check if the condition cures itself miraculously, not driving without a VR. You can test drive it avoiding going up 1700/2000 rpm but just to check if it's the VR, then plug it right back and confirm wether it should be replaced or not. As of the grounds, something must be shorting as Ed CT says. Another possibility is as Leroy08 says, a bad battery.

[Ed CT]

Yeah I was suggesting unplugging the VR and check if the condition cures itself miraculously, not driving without a VR. You can test drive it avoiding going up 1700/2000 rpm but just to check if it's the VR, then plug it right back and confirm wether it should be replaced or not. As of the grounds, something must be shorting as Ed CT says. Another possibility is as Leroy08 says, a bad battery.

If un-switched accessories still run (cabin lights, etc.), I am with you jicaino on the Iggy Switch needing replacement.
OP - how many miles on your car? If the IgSw has never been replaced, it may be worth doing for about $100 (IIRC). If it were me (time + car reliability is a premium and $100 is expendable), I'd just replace the Ig Switch. It's a good PM measure anyway. Most of them eventually go bad and do all sorts of weird stuff.

[trevzor4242]

If un-switched accessories still run (cabin lights, etc.), I am with you jicaino on the Iggy Switch needing replacement.
OP - how many miles on your car? If the IgSw has never been replaced, it may be worth doing for about $100 (IIRC). If it were me (time + car reliability is a premium and $100 is expendable), I'd just replace the Ig Switch. It's a good PM measure anyway. Most of them eventually go bad and do all sorts of weird stuff.

146k miles... So it's definitely possible, I just don't want to throw money at the problem. Im not having the weird visor issues like most people. And my logic that the radio lost all power not just the switched turn on means the key switch isn't (the only thing) at fault. Right?

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[trevzor4242]

I've tried jiggling the fuse boxes as suggested and it had no effect. Batt terminals and explosive cap are tight. All ground terminals I've found on the body are fine and tight too.

I'm willing to try the VR idea but the thing that makes it so hard is it's such a sporatic problem that it probably wouldn't even occur anyways without a lot of driving. For example it went away for at least a month til it occurred again and I recorded the video.
So running it in the garage for a few minutes with the VR unplugged without issues wouldn't be conclusive enough to say it's the problem.

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