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Seeking input for a frustrating problem. I've done deep searches on this forum (and others) for a similar issue to no avail.
2005 E55 Wagon. PO did some minor-ish mods (long tubes, straight exhaust, VRP pulleys/beltwrap kit, split cooling) but is otherwise stock. While driving one day got the red battery fault on dash, consumers shut down etc, burning smell under hood, limped it back to the house. Had to trickle charge the battery back. After charging the battery the car started no issue, but was not charging above 12.3V on dash or at battery with multimeter. Work schedule prevented me from addressing further myself, took it to local indy shop that had previously done a radiator and VCG replacement for me without issue. I told them it likely needs an alternator, but they wanted to fully evaluate first. They had the car for a week, hemmed and hawed, tell me over the phone the alternator is fine, can't find anything wrong with the car, come pick it up. On the paperwork under recommended service they say "replace alternator" .
Feeling like I was taking crazy pills, I ordered an alternator from FCP (factory Bosch reman, FCP says new alternators are NLA) and decided to do it myself. Not the most fun job in the world, but persevered. Alternator that came out of the car was a factory Bosch reman (AL0826X), and was totally destroyed. Diodes and surrounding plastic were incinerated.
Got everything buttoned back up and its putting out 13.8-14V at idle whereas before it was battery voltage and dropping. Great! Revved it a bit to get the thermostat to open and get some flow through the heater core after bleeding and the dash lights up with ABS, ESP, Brake malfunctions etc. and low battery voltage. Checked voltage on dash and with multimeter at the battery. At idle its a rocksteady 13.8-14.2V. If steady soft throttle is applied, it stays in that range. If you quickly rev and let off the gas, it spikes to 15.5-17V and sets off the warnings (plus a relay audibly clicks in the driver rear SAM with everything taken apart back there). Thought perhaps it was a bad (new) VR, and I had already ordered one blindly hoping that was the original issue, not the alternator itself. Put the new regulator on and same result. As part of this whole process I put brand new AGM auxiliary and main batteries in the car, but the batteries that came out (wet cell MB) tested fine at Autozone.
I have checked for battery voltage from the positive battery terminal line, to the pre-fuse block in the passenger footwell, and at the B+ terminal on the alternator. No apparent drop. Wire brushed and ensured all connections are tight. Alternator is grounded based on multimeter. There is ~12.1V at the L line (I think anyway, blue with white stripe) in the connector at the voltage regulator with key on. With the B1 terminal disconnected in the driver front SAM with the car running I couldn't get a voltage reading from the blue line (which I'm presuming is DFM and 'should' be communicating alternator voltage), but did note that the dash readout went to battery voltage with this disconnected, so I'm ASSuming that the terminal 61 circuit is good. I tried resetting the BCM by unplugging and letting it sit and plugging back in. No change.
I'm at a loss. Has anyone experienced anything similar? Two bad brand new voltage regulators? Seems unlikely. Bad BCM? Could this just be a **** reman alternator that is internally shorted/going full field under throttle and the VR can't control it? Not thrilled to think I have to do this job again due to a crappy new part, but I guess I'd prefer that over some other nebulous electrical gremlin that is above my pay grade to suss out... Looks like a truly new Bosch (AL0826N) is, in fact, available but is now made in China, so I'm still leery of getting burned again.
Might have a bad regulator on the alternator. If it were me I would throw a new regulator at it as it can done in the car fairly easy. You would be spending even more money but you wouldnt have to pull it again.
I actually keep one in stock since they are popular to go bad.
If it doesnt work you know it is something else. Or...send the alternator back to FCP
Might have a bad regulator on the alternator. If it were me I would throw a new regulator at it as it can done in the car fairly easy. You would be spending even more money but you wouldnt have to pull it again.
I actually keep one in stock since they are popular to go bad.
If it doesnt work you know it is something else. Or...send the alternator back to FCP
Agreed; I already did that and put a new regulator on the "new" alternator, with no change in outcome. I'm not opposed to trying another regulator seeing as its doable on the car, but what are the odds of having two new regulators (Bosch, made in Hungary) be bad?
Not the regulator then.
Battery control module would be my next thought. On my 05 Sedan its in the trunk right near the battery so not sure on the wagon but must be the same I would think.
I am not sure of the testing procedure for that and I don't like to throw parts at a problem but other than the ECU doing something really stupid I would go for a module and see since they are easy to do. Should not have to be programmed ???
If Birdwell chimes in he is far more "Electrical" wise on this forum so maybe he can help.
I had the same over charge error after new alternator was installed. Refused to check cable and connector while troubleshooting cause I swore it was tighten down correctly. Gave in and found cable was slightly loose.
I had the same over charge error after new alternator was installed. Refused to check cable and connector while troubleshooting cause I swore it was tighten down correctly. Gave in and found cable was slightly loose.
I had this suspicion as well, but man I tightened the bejeezus out of every connection. Do you remember which was loose on yours? Was it the B+ on the alternator itself?
I put the replacement BCM in the car (it had a new style BCM, interestingly with a 2004 date code on it, and the car is an '05 so I'm assuming it was original), but no difference. It's still overcharging when revved to 3k rpm and it spikes to 16+ volts right when you let off the throttle. So frustrating.
Well this got interesting...I thought for sure BCM would do the trick.
Long shot here.....check fuses in F33- It's a "pre" fuse box in trunk against the wall near the spare tire and battery,
there are two 200amp
two 150 amp,
three 5 amp
and one 40 amp
check fuses in F-32 "Front Pre Fuse Box" near what "I" call the "other" BCM Location -Passenger front foot well. That's where the main power cable comes into the car
four 40 amp
one 50 amp
two 150 amp
N82 or Battery Controll module monitors altenator voltage on terminal 61 through CAN B so we might need to start chasing that if all the fuses are good.
I am asumming an "open" fuse will create a "run away condition" voltage spikes so check all of them before moving forward.
I could be very wrong but I would want to know all these fuses are good first.
Unfortunately when it comes to alternators on european vehicles, it's a hit or miss with FCP or any other after market vendor. Even if it's a Bosch or Valeo unit.
We had two cases at the shop on a 2003 E55 and 2007 R63, both with overcharge issues using a Bosch alt from FCP. Clients sent in for a full refund (FCP knows about this issue and has great customer service, getting your full refund won't be a problem). Both vehicles ended up getting a genuine alt from the dealer and that got everything back to normal operation.
I can also add to this where a car in my Ford shop had constant miss fires right after the owner installed an alternator,which we found out days after chasing the miss fires, and found that the alternator was creating a magnetic field around the coils and creating havoc.Installed a genuine Ford alternator, problem gone.
Well this is all very interesting information, and fits with my initial suspicion as the charging system was subjectively fine before the initial alternator failed. Pretty lame that even a factory Bosch reman is garbo. I bought a 'brand new' Bosch and it's made in China, so that will be getting returned. Will call my local dealer today to see if they can get an MB alternator.
SICAMG, the front pre-fuse arrangement all looked good when I initially had things apart, but didn't assess the rear. Haven't had a chance to dig in to things the past week, between weather and work. The knockoff Star diagnostic system showed up though, so at least I'll have that to probe further, but I still feel it's the alternator at fault.
I used to have a company that rebuilt starters and alternators. They could do anything you wanted in your housing with the best internal parts,any amperage,pulley and even voltage. They are long gone,like everyone else, which sucks.
Well, to wrap this up and hopefully help someone else in the future, @MosaicMTech was on the money. I finally was able to repeat the job with the factory MB alternator, and the car runs perfectly with system voltage sitting at a rocksteady 14.1V +/- 0.05V regardless of engine speed.
Of note, the subjective quality and fit/finish of the MB part is notably superior to the Bosch unit. The B+ stud is about 3 times as long. I found it interesting that the factory unit has a different voltage regulator than what is sold as the replacement (BR14-H instead of BR14-MO) - not sure what to make of that.
Moral of the story is always install OEM parts on these cars.
R.K.
Absolutely. Some sources list this part as NLA from MB (I should've called the dealer first) and the cost is a stark difference between the two: $1k for the MB part out the door with core charge (they won't take a Bosch as a core, only factory MB) and TX sales tax, but when you're talking about the labor involved with this job, the extra $700 is worth it to avoid the frustration.
I chuckled when I saw this photo. I've had the same feeling multiple times when working on my E55. I could swear MB laid an alternator and the driver side motor mount on the start of the assembly line and then built the car around them...
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
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Checked voltage on dash and with multimeter at the battery. At idle its a rocksteady 13.8-14.2V. If steady soft throttle is applied, it stays in that range. If you quickly rev and let off the gas, it spikes to 15.5-17V and sets off the warnings (plus a relay audibly clicks in the driver rear SAM with everything taken apart back there). Thought perhaps it was a bad (new) VR, and I had already ordered one blindly hoping that was the original issue, not the alternator itself. Put the new regulator on and same result. As part of this whole process I put brand new AGM auxiliary and main batteries in the car, but the batteries that came out (wet cell MB) tested fine at Autozone.
