6spdcoupe

Yes, yes, yes I have searched ad nauseum ! Found a lot of helpful things but the majority I have already done or recently did.

Car is a '06 E55, 92k

The short story .. While getting gas one day the Red light came on, all accessories shut down. Started driving again and it went off. A day or so later it came back, then off.. since then (a few weeks ago) it does this randomly and with absolutely no specific 'trigger'. AC/radio/etc off- still does it. WOT or parked/idle- does it.

I monitored voltage and when 'it' occurs I go from 14.2 down to mid-high 10.
Front and rear batteries are new and good.
Alternator is charging properly.
Regulator was changed approx 1500-2000 miles ago.
Dual battery relay was just changed.
BCM was flashed/updated a couple years back (approx 2k miles).

I have another regulator to swap in, I do plan on swapping it, just for the sake of mindset but looking for any other thoughts...

I Will change the BCM if general consensus leads me there, but would like some reassurance before throwing more good money after bad.

I do also have the dynamic seat pump problem - runs relentlessly for approx a minute during wakeup. Just discovered this and will address but having the car running (electrically) properly first is more a priority ! Not sure if it's relevant, but worth mentioning.

StarvingArtist

Always fix known problems first. It's surprising how often it leads you were you need to go. 10/11 volts is really low for a good battery. Mine was holding 13 when I forgot to plug the VR back in.

Critter

Off hand I would look again at the batteries, mainly the rear battery for voltage when the car is off, 12.5-12.7V would signify a fully charged bat. Also just as important is the terminal connections, remove and clean both the bat term and the cable term and assure that when you retighten them try to twist the terminal, as sometimes they are tight but the terminal is smaller than normal and the cable can twist with minor force, a bad connection will cause grief. As far as you say you have a good battery but I had an issue years ago where the terminal connection inside of the battery from the plates to the terminal were broken and only one plate was connected, well when that failed the spark that was created when trying to start the car exploded the battery. For piece of mind put another main battery in and retest.
Agree with StarvingArtist it takes a lot to get a good battery to 10volts, was this with or without the car running?
Check the connections. Was the changed out regulator a Bosch unit? or aftermarket?
Are you getting the voltage readings off the dash or directly off the battery, off the battery terminals will assist with the diagnosis.

Exotic-metal55

If the regulator has not been changed yet, then you will be suprised at how low the copper arms will be worn VS the new one.

desired_speeds

I had the same symptoms as you on my car until the car just died one day. It was the voltage regulator

6spdcoupe

Sorry, not sure I follow, which known issues are you referring to ? The low voltage was on the cluster while driving. If you thought I meant the battery went that low when off, then I surely understand what you mean.

6spdcoupe

The new battery was done about 3 days ago - old battery also tested as good, but wanted a piece of mind so to speak. Terminals are clean and tight !

The drop to the low-mid 10V was on the cluster while running/driving. I am sure I can run a line into the cabin and read from the battery as well.

Unfortunately the regulator that was changed was to a Huco, which recently I found is a bit frowned upon. I have the Bosch replacement here now.

Out of curiosity, where does the cluster actually read voltage from ? Battery, BCM, Alt ?

typhoon43

Get the Bosch regulator in and report back. That's the quickest/cheapest test. You say the alternator tested fine. Unless you pulled the alternator out and brought it in, I wouldn't trust that test, as you yourself say the voltage will be fine one minute and then dip out of nowhere. You could have tested when it was in a "good mood". Good luck man. I had the same issue and it was a combo of the voltage regulator AND the 6 month old front battery I had gotten off amazon. It failed a load test and I was shocked. That's what I get for going with a "cheap" front battery.

6spdcoupe

Agreed, I was just here planning out what else could be going on as I have very little good luck !

You're absolutely right. Both the battery and alt passed load and charging tests, but in vehicle and could have been a few 'good mood' times. Although if it were the alt, wouldn't it be the regulator causing the 'bad mood' ? Just spit balling ..

StarvingArtist

Your known electrical problem=dynamic seat pump.

das eighty

Could you elaborate a bit on this? I just swapped both batteries and after sitting still or in traffic for ~10 minutes, I'll get the battery warning. I'm also experiencing issues with the driver seat base; front height adjustment doesn't seem to work, just clicks and stays at the same height.

6spdcoupe

Do you really think it is relevant though ? Serious question, no sarcasm intended. Seems like the exact symptoms tbal had here: https://mbworld.org/forums/w211-amg/...t-working.html but no melted lines/ports/etc that I could find in a brief check. Could I not just pull the pump fuse for the sake of troubleshooting the bigger issue ?

Critter

Yes for peace of mind pull the fuse for the seats, that being said if that was the issue when the battery was pulled down to 10V and probably 800 amps or whatever your battery is rated for the result of a short then the wires affected would light up like a Christmas tree and there would be copious amount of smoke as in call the fire department.
Try this, shut off all accessories, radio, AC, everything you can, then start the car and measure at the battery the voltage 13.8-14.2V should be in that range.
Now shut off car and turn everything on with the key in the on position but not start the engine, so the radio will be playing, the ac button light on, blower on high, you get my point, now start the car and remeasure the voltage at the battery this reading should be the same as the before reading. If it is below 12.V /whatever increase the rpms of the engine to around 1000rpm and remeasure this time the reading should be 14.1-14.2V if not the regulator is not functioning properly


As also stated if not a Bosch regulator then install one first. MB cars seem to know when a different reg is used and the alt does not respond well.

Critter

das eighty- voltage regulator, the car is running off the battery as the alt is not supplying power to recharge and sustain the battery. Sitting in traffic at idle you would see the voltage drop off, triggering the warning/fault.

6spdcoupe

I didn't figure it to be relevant, but at my wits end I was willing to give anything consideration !

Yessir, did that and all checked out well. Aside from the 'hiccups' or bad moods it seems to have, it stays pretty steady at 14.1/14.2 both at battery and cluster. Which would seem to lead directly to the regulator not doing a proper job of, well, regulating ! Admittedly I initially dismissed this as it was changed awhile back, but only recently found that it was changed to a sub-par Huco.

We have/use both of these here and everything seemed to pass fine:
http://buy1.snapon.com/catalog/item....roup_id=682185

http://buy1.snapon.com/catalog/item....store&tool=all

STAR and my Maxidas also found nothing odd, so a 'hiccup' just may very well be the proper terminology ! lol

das eighty

Thank you sir, that was my next step. I'm considering doing the alternator too, depends on what I can pick one up for. Two birds, one stone.

6spdcoupe

The alt is a quite larger task than the regulator. Usually not the issue either. IF you do go that route though .. do Not go with a refurb.

6spdcoupe

Well, I hope I don't screw myself by saying it, it seems like it was the regulator. Not much a drive today but so far, so good and zero issues.

6spdcoupe

It's a damn shame, that Huco was less that 2k miles. Learned my lesson and sadly was dismissing it since it was still fairly new.