HELP!! Bad Voltage Regulator?

[we350z]

Hoping some folks here can give me some guidance.

Recently, I started noticing some strange behavior on my X5 with regards to the electrical system. The first strange thing that happened was that one time when I parked and turned the car off, my Umnitza Angel Eye's (wired to the ECU) did not turn off after a couple seconds like they normally do. Disarming and re-arming the security alarm did not fix this - I had to put the key back in the ignition, turn it to ACC and then remove it again, only then did it shut off like normal. Next when I tried to start the car again, when I turned the ignition first it clicked and did nothing - then i tried again and it sluggishly started (something I have noticed degrade over time). I also noticed my AE's flickering a little bit but then that went away.

While driving home I started paying close attention to the voltage readout on my ScanGuageII unit thats connected to the OBDII port. It was bouncing around erratically quite a bit, and dropping below 12V when I came to a stop. It sounded like the whole thing was straining so I turned off the heat, headlights, NAV/boardmonitor, turned down the dash lights, etc...

My immediate thought was that something was wrong with the alternator. I noticed several times that the headlights seem to dimming/fading in conjunction with the dash lights but they would only do this momentarily then come back. Things seem to be operating much better at highway speed. When I got back on the main road to my house there were several times I swear I saw the dash lights and headlights completely "blink" on/off for a split second.

While outside of the car with the engine still running I thought I could hear a strange whining sound but that might have been my imagination.

I was really worried because the next morning I had to drive back home from Tahoe to SF, about 220mi. I hooked up my battery charger to the battery to make sure that I would be leaving with a full charge. I disconnected my AE's and my sub woofer amp, and turned off all accessories to minimize the draw. I renewed my AAA membership because I thought there was a good chance I would run the battery completely down before I made it home.

During the drive home, even at highway speeds 55-85mph the voltage still wandered around a lot - typically from 12.4V - 13.5V and sometimes moved as much as 1V in either direction. Is this normal? I was told that when the engine/alternator is running the charging system should regulate the electrical system to be at a constant 14.4V? Upon stopping the voltage almost always nose dived below 12V than came back up to fluctuate between 12-13V.

So wondering:

1) My BOSCH battery is approximately 4 years old - 2 of which was spent in AZ with extreme heat. I have also run it down quite a few times working on the car, leaving the car sit for long periods of time, etc... Worth it to try replacing it? Maybe it is just struggling to hold a charge? My battery charger is really good tho (Schumacher SCUPSC12500A) and charges is to 100% on 2A/15A without entering de-sulfate mode or indicating the battery is bad.

2) I recently installed LED turn signals in the front when I installed my AE's. I have not yet spliced in the capacitors to normalize the ECU voltage check (to prevent OBD/cluster error messages) - could this be causing some problems?

3) My understanding is that alternators either work, or don't work. there is no in between. If it were dead my voltage readouts should never go above 12V I would think. So assuming this cannot be the case - that it can't be "going bad".

3) Is it possible that just the voltage regulator on my alternator is bad? Is there anyway to just replace this part without removing the alternator? How long can I go before it's completely shot? Guessing it will fry the battery before then. If you have to remove the alternator anyway I would just replace the alternator as well.

About a year ago I replaced my water pump successfully and it is still working great, so I am confident that I could replace the alternator as well. I would rather avoid the hassle and labor of doing this if possible. If I do end up having to replace the alternator and voltage regulator, since the alternator is water cooled - is it necessary to drain the entire cooling system or can you just remove it and top off the coolant after re-installation? Or will I have coolant gushing out all over the place if I do that? My only other concern is I don't really have any airtools and I hear the bolts securing the alternator are loc-tited...

Wondering if it makes sense to take the truck to the local indy shop and have them look at it and give me a quote. Not sure I want to go through all the hassle again - but saving $1400 in labor as I did with the water pump does sound attractive.

[we350z]

So - I did some hunting and found some reman BOSCH OE units (MPA 15479) that are pretty inexpensive:

partsbin - $171.80 (use code "WELCOME5")
eBay - $178.46 (with eBay bucks)

Prob just gonna go with one of these. Assume I will need a new o-ring but otherwise i should be good to go. Replaced both belts when I did my water pump last year.

[Dan Fowler]

You definitely are doing diligence on your problem. Good job. There are plenty of posts here supporting how tough BMW is on a battery, and I have that experience too. Mine is a 06. In 09 I had to replace the battery. Soon after I had the alternator replaced at the stealer. Now the battery is showing signs of weakness again so I will be back at Pepboys for another battery soon.

When the alternator/regulator started failing, I had ugly gremlins popping up everywhere there was electrics. Really. It was bad, and I got stranded by failsafe twice. Since alternator replacement (about 100k miles ago) all has been well.

Some guys on here may have specific technical advice for you. I can only offer real life experience to the tune of about $1100 bucks. Good luck.

[BrianX54.4is]

In my experience I have never seen my voltage go beyond 13.6V and it does fluctuate as low as 11.9 when slowing to a stop before recovering again so I think your readings are "normal". When my battery charge gets low I also experience a few gremlins like spurious warning lights that soon clear and headlights staying on momentarily after shutting down the engine.

My thoughts are 1 step at a time starting with the easiest / lowest cost job.
1. Your battery owes you nothing (4 years service with some deep discharging and subjected to high temps). Change it out.
2. Monitor for improvement - if charging/battery drain is the issue, your problems will be back within a couple of weeks.
3. Check for excessive drain on the battery when the car is shut down. After 3-4 minutes the current draw should be no more than 50mA. (The car can still draw 3Amps or so for the first few minutes after shutting down untill all controllers and equipment have shut down to "sleep". Some electrical mods can prevent the aux electrics from "going to sleep" causing battery drain so check all your aftermarket electrical mods.

I doubt that the votage regulator is your problem (as it is regulating and you do not have the charging warning light!) so avoid the alternator changeout untlil the above steps are done.

[RickM5X3]

Originally Posted by we350z

During the drive home, even at highway speeds 55-85mph the voltage still wandered around a lot - typically from 12.4V - 13.5V and sometimes moved as much as 1V in either direction. Is this normal? I was told that when the engine/alternator is running the charging system should regulate the electrical system to be at a constant 14.4V? Upon stopping the voltage almost always nose dived below 12V than came back up to fluctuate between 12-13V.

I monitor voltage every now and then using the OBC test function. When my alternator was on the way out, voltage was always in the 11-12V range.

With a good alternator, it never dips below 13.4 or so and usually is 13.9 to 14.1V according to the OBC.

To view the OBC test:
) Key to ignition pos 2 (no need to start engine).
2) Fasten the seat belt to get rid of the “Fasten Seat Belt” message.
3) Press the right button on the instrument panel, and hold it until “TEST-NR. 01″ comes up (5 to 10 seconds).
4) Press the left button on the instrument panel, and the vehicle id comes up (last 7 digits of VIN).
5) Add up the last 5 digits to get the “unlock code”, e.g. the unlock code for “AB12345″ would be 15 (1+2+3+4+5).
6) Repeatedly press the right button until “TEST-NR. 19″ appears.
7) Press left button -> “LOCK : ON”
8. Repeatedly press left button until “LOCK : xx” appears, where “xx” is your unlock code.
9. Press the right button. All modes are unlocked now.


Test 9 gives the voltage. My personal favorite is Test 7, which shows coolant temp.

[we350z]

Thanks guys:

@Dan Fowler - definitely agree that the X5 E53 (and BMW's in general) are power hungry with all the accessories they are running. On top of that I am powering a 300W RMS MTX Thunder 5302 sub woofer amp, Umnitza Predator Chromium V2 Angel Eyes, Scosche Bluetooth adapter, V1 Radar Detector, and a Phone Dock. No light load. To my knowledge the alternator has never been replaced and I am at 84,500 miles. I will have to double check the service records to be sure.

@BrianX54.4is - Interesting - it had crossed my mind perhaps the battery itself was the issue since the starting has become more lethargic and the the recent "click" when trying to start. I agree with your thought process about switching out the battery first. It's not reasonable to expect more than 4 years out of the battery, especially with abuse. It has been almost 4 years since I replaced the battery last. Eventually the cells are going to be damaged and the CCA's will decrease. Even after charging (supposedly to 100 percent, but I don't trust the digital readout on my charger) the cranking didn't seem that strong when starting the car. Excessive battery hasn't really been a problem. I have even taken steps to prevent battery drain completely by installing a Battery Brain (see my post on this). What points are you testing the current draw from? I do know that If I let my car sit for 3-4 weeks without the battery disconnected there is a good chance the battery will be (near) dead.

@RickM5X3 - I do know about the OBD diagnostic menu (my ScanGuageII does the same thing). I should check that it is consistent with the guage but I would be really surprised if it was. I'm going to get a new battery and monitor.

Thanks for the suggestions guys - totally no harm in trying a new battery and avoiding significant cost and labor. Worst case scenario is that I spend $100 or so on a new battery that I didn't really need :-) If it fixes the problem that is great if not the alternator replacement job is very doable.

--Thanks!

[we350z]

Pricey, but decided I'm going with this bad boy:

Braille Endurance Group 49 AGM Battery



Part Number Details

Braille Battery Part Number B10049
BCI Group 49
>150 Reserve Capacity (RC)

2,856 pulse cranking amps
1,520 cranking amps
1,115 cold cranking amps
100 amp hours
12V
Right-side positive terminal
13.9" long, 6.8" wide, 7.5" tall, 58 lbs
Braille Endurance Battery: Part B10049

[we350z]

Checked with 3 local indy shops and if I provide the part the labor would be around $350 including the cooling replacement.

Good deal or no? I think for that price I may consider avoiding the hassle.

[we350z]

Well this is bizarre. I think the problem may have mostly gone away. On my trip up to Tahoe yesterday I rarely ever saw the voltage drop below 13.5-13.8V almost the entire trip. I think I few times, when coming to a stop I saw her in the high 12's briefly.

I don't know what's going on but I will continue to monitor. I ordered a new Braille battery already so I will be installing that anyway. I think my BOSCH is still kicking strong tho - I guess I will just turn it into a shop bench battery or something or power a mobile sound system for one of the fine street events we have here in SF :-)

[diyanich]

Don't forget to register the battery,I assume you know what the process is about.ECU needs to know that it's a new battery that goes inside.

Originally Posted by we350z

Well this is bizarre. I think the problem may have mostly gone away. On my trip up to Tahoe yesterday I rarely ever saw the voltage drop below 13.5-13.8V almost the entire trip. I think I few times, when coming to a stop I saw her in the high 12's briefly.

I don't know what's going on but I will continue to monitor. I ordered a new Braille battery already so I will be installing that anyway. I think my BOSCH is still kicking strong tho - I guess I will just turn it into a shop bench battery or something or power a mobile sound system for one of the fine street events we have here in SF :-)