e55aed

TLDR: 3rd alternator on E55 has burned/melted in 4 months each after a little bit of enthusiastic driving (going 75% throttle from a dig), have no idea what is causing failures to happen. Alternator purchases + labor to replace is not cheap hence desperate to find a long term solution. Any help/ideas welcome. Update is that Alternator 3 not burning anymore, voltage back up to 14V at WOT, but 12-12.5V at idle + weird sound from trunk (see video)

Backstory/Facts:

1. 2005 E55 with 80k miles / 130k km. Owned since 115k km. Fully stock except for Bosch 010 IC pump upgraded in August 2020
2. During COVID car was not started for ~15 days sometime in early June 2020. Was completely dead, so I jumpstarted the car using another car (Volvo XC60) - I did not know one should not jumpstart a Benz
3. After jumpstarting the car a day later, got an ESP and Speedtronic Inoperative warning message, car suspension also firms up while errors occur. A STAR scan says defective Steering Angle Sensor but did not replace it yet (have already swapped the brake light switch to no avail)
4. Other items that need fixing on the car: FL control arm bushing, FL wheel bearing vibrating, and engine/trans mounts (though engine mounts not severely compromised)
5. Auxiliary battery 8years old but as far as I understand it is just there for backup hence impossible for it to be the culprit (https://manualzz.com/doc/24441931/w2...battery-system)
6. Android Heat unit installed using MOST Fiber Optic interface to run with stock amplifier and HK speakers. Went bad in May 2020, replaced under warranty mid-June 2020

Alternator #1 failure:

1. The original alternator went out (burning smell and black plastic) in August 2020 during a regular drive after car was serviced and had oil change. Voltage readout changed from 13.9V to 12.0V all of a sudden (I have an Android Head Unit that shows voltage all the time).
2. Accordingly I had the alternator replaced with a Bosch unit (same specs as the factory alternator (pics below) and also replaced the battery (Bosch AGM) for good measure

Alternator #2 failure:

1. Here is where things gets interesting. The new Bosch alternator starts smelling burnt in mid-December 2020 (just after 3.5 months!!!) after I do an enthusiastic launch from a dig, and indeed the voltage is down from 13.8V to 12V. I take it to the same garage who fitted it and they say the new alternator must have been a faulty one as well (they confirmed this after checking something under passenger side footwell). Problem is suppliers where I live do not offer warranties on alternators so I am out of pocket.
2. This time, I skeptically harvest an alternator out of a M113k engine I found in a used spare parts store, and got it installed on December 15th, replacing with the recently burnt Bosch alternator which I bought brand new in August 2020............
3. All was well with 13.8V
4. I was looking at the voltage more often than the speedo at this point, and noticed while secondary air pump was on during startup the voltage was 13.6V, and sometimes when reversing the car it got as low as 12.9V

Alternator 3 failure: (apparently still works)
Yesterday, after a bit of enthusiastic driving shortly after starting the car, the same thing happens, alternator burning, smelling, and voltage drops.

I am honestly at a loss of what to do now. What am I doing wrong/not noticing? If anyone could help, I would be eternally grateful to you. Love this car, aside from these electrics...

Thank you.

UPDATE 7 Feb 2021:

1. Parts numbers of alternators installed were fine (the Bosch part number coding is slightly different to the MB part number but they are the same exact part (confirmed with Bosch and MB Dealer) - the new MB part number (A0131548502) was an updated part number for the previous MB one (picture above) that was installed on the car, confirmed with EPC.

2. Star does not show any faults BCM

3. Left the car sitting for a couple of weeks, then charged the battery and started the car up and gave it to a mechanic who I could trust: they have checked the wiring (ground wires, etc.) and everything looks ok, AND the alternator does not have that burning smell anymore! The voltage is now 12.5V at idle, and when pressing the throttle it goes up to 14-14.2V and once off the pedal it goes back to 12-12.5V. This has baffled everyone - how can a burning alternator suddenly be charging the car at high throttle, and why does it drop down to 12-12.5V if not on WOT? Not to mention there has been no battery/alternator warning message in the gauge cluster at any point during this alternator feast.

The mechanic has told me they have cleaned the ground connections, and I have taken the car back to test drive it for a short while to see what happens. It seems like this is an intermittent issue that destroys alternators when it happens but cannot be traced likely because of its intermittency. The phantom alternator #3 being able to charge the car again at WOT makes no sense either (the burning smell is indeed gone and it was pretty bad and noticeable earlier).

Plus, I have just noticed a whining noise from the trunk

See video of the voltage issues and this trunk noise here:

You Tube

Failed alternators 1 and 2



Alternator 3 (failed yesterday)

machild

I have no idea what the issue is, but I do note (and you may have already sorted this out) that you have three alternators with three different Bosch part numbers. Next, have you run a deep diagnostic check using MB Star including the system's various tests and actuations? Does the car have any aftermarket items added like stereo, heavy duty water pumps, lighting and so on?

GinDistiller

I second the concern around 3 different part numbers, talk to a dealer and provide your VIN and make sure you get the correct part # for your car.

And yes, STAR test for codes is a must, these cars have battery control modules and things that can code if there are issues.

Do the pulleys and accessory belt look ok? Make sure those aren't seizing and slipping (can also cause a burning smell).

Ground and wire connector to back of alternator ok, and the rest of the engine grounds?

Lastly, I'd also test the battery itself and make sure to check all fuses in all panels and locations if you haven't already.

Oh, and don't worry about the ESP error after starting it, that is due to the battery being dead. You're supposed to turn the steering wheel (stopped, engine running) from lock to lock several times so it can learn the steering angles. That always happens after a battery disconnect.

Best of luck!

e55aed

Thank you machild, Indeed I did notice the part numbers, however I would have though that would be to do with the different times in the past each alternator was made over the years. They common denominator amongst all 3 is the 180A output that is critical which should mean they should work fine.

Everything on the car is stock (except for the audio head unit which was fitted back in September 2019 (stock speakers/amp etc.), and the Bosch 010 IC pump (very common upgrade for the E55) so I wouldn't think those would cause an issue.

Have done a Star regular test back in August before the 1st alternator went. The main thing of notice was several under-voltage warnings and a defective steering angle sensor warning. No actuation tests etc. done (mechanic charges $100 just for a STAR run here!)

In any case I've never heard of an electrical items in the car going so far as to cause serial alternator malfunction, though I could be wrong.

Thanks again.

e55aed

Thank you GinDistiller,

Sure will check that with dealer and get the exact part (the picture with the Mercedes logo was the original alternator hence a good baseline assumption).

I'll probably buy a STAR system to be honest just for convenience and given the amounts everyone charges for a simple diagnostic run.

Pulleys/belt look ok/mechanic said they are fine. Burning smell is most likely that plastic seen oozing out of the alternators.

Ground and wire connectors to alternator should be ok, mechanic did it in front of me when fitting the latest. I will do a continuity test to confirm whether grounding is fine.

Battery is brand new but sure will check the fuses (though why would a fuse that is out mess with the alternator? Sorry new to all this!). The secondary battery is 8 years old but as far as I understand it is just there for backup hence impossible for it to be the culprit (https://manualzz.com/doc/24441931/w2...battery-system)

On the ESP unfortunately I was told this but despite doing it the error does not go away, have tried everything and don't want to start throwing money at the problem until I know the fix.

Thanks again!

GinDistiller

Yeah, it's unlikely a fuse would cause this but with so many interconnected control modules that can be sensitive, plus having jumped the car, it never hurts to check

You're correct the aux battery wouldn't cause this.

Maybe once you have a part #, look into any online sellers who carry a warranty? I can't remember which one but I think either FCP or ECS offer lifetime warranties on some of their parts. Who knows, it could just be bad luck?

machild

Yes, FCP provide lifetime warrantly on parts they sell.

bbirdwell

You can jumpstart your car, you just need to have the key fob out of the ignition switch when you connect the jumper cables. If you have Keyless-Go, place the key in a Faraday cage pouch or keep it a minimum of 2 meters from the car.

If the key fob is in the ignition when connecting jumper cables the circuits are energized and the arcing can blow fuses and/or damage modules.

Buy your own diagnostic system; it saves time and will pay for itself in a few uses.

e55aed

Thanks. Went to the dealer. Part # is A0131548502 and nowhere to be found. Got quoted $1,600+ for just the part (labour is extra) - lol.

Did a battery continuity check to check the grounding. Disconnected negative terminal then read voltage across battery terminals (12.4V), then voltage across negative wire and negative battery terminal (11.6V) - understand that's within limits so grounding shouldn't be an issue.

Will order a Star system in any case but will take a while to reach me (20+ days) which I do not have time for.

Found a garage who will offer a 1 year warranty for a newly installed alternator, quoted $800 all in. Think I will go for that for peace of mind and hope 3rd time's the charm...

FCP Euro is restrictive for me given I live almost halfway around the world from the US and shipping is too expensive.

e55aed

Thanks! I do not even remember if I had put the key in before connecting the jumped cables. I also jumpstarted another car while the E55's engine was running so who knows what that did.... Of course did all this before knowing you can't just do that on a Benz. Will definitely check the fuses/do Star diagnosis once I get the system - need to find a decent one and order it online.

bbirdwell

Shipping may be expensive but you can always offer to buy me a round-trip airfare ticket and I'll gladly deliver you a rebuilt Bosch alternator for free!

Seriously, now is the time to, as we say here, "Measure twice, cut once". I wish you the best with your car.

M5 LOL

over tightening the belt? this can smoke the bearings in a hurry.

MartinWake

Bringing this thread up again but this seems to be happening to my CL55 too.

not sure if my car keeps burning up the alternators or if the one I bought was just bad. I bought an oem alternator off ebay with warranty and it had been really go so far but now after 3 months I noticed a plastic burning smell from the engine bay exactly like the old alternator did then I check the voltages on the torque app and I can see them dipping into the 11's a lot I am pretty sure another alternator died. I started the warranty process but why do you think this happened again?

machild

Was the alternator you installed a remanufactured unit or was it new? Have you done a full scan of the car with MB Star to see if any faults have been set?

MartinWake

The alternator is a used one with warranty oem, Yes the car had been at a good shop for another electrical issue and every inch of wire / ground wire and modules had been checked over and over. The ecu was taken apart to check for corrosion along with other modules that usually fail. Everything is in perfect condition. They had star and autel connected checking it over and over. They fixed the original electrical issue which was really hard to find other then that the car is perfect just this alternator thing again.

machild

Then it looks like you have a worn out alternator/voltage regulator. Alternators can be tested out of the car to determine exactly what is going wrong with it - whether a simple voltage regulator or a bad diode and such. May be worth it to find out what is actually wrong with it. If it is only a voltage regulator it may be easier and quicker to have the car back in use to just replace it. Don't use junk, install a Bosch VR.

MartinWake

I will probably have to send it back for the warranty process but I am very sure it is not the voltage regulator, on my old alternator when I started smelling the burnt smell and low voltages I noticed the bronze part starting to turn black now this one is doing the same thing. Also on my previous alternator I removed the voltage regulator and it still has lots of life left by how long the two legs are. Kind of annoyed but if it is just the alternator which I suspect it is then it would be covered under warranty. It is a oem unit from a 2005 CL55 amg.

e55aed

UPDATE - (bringing original thread back to life with quite a strange update):

1. Parts numbers of alternators installed were fine (the Bosch part number coding is slightly different to the MB part number but they are the same exact part (confirmed with Bosch and MB Dealer) - the new MB part number (A0131548502) was an updated part number for the previous MB one (picture above) that was installed on the car, confirmed with EPC.

2. Star does not show any major faults in electric system/BCM

3. Left the car sitting for a couple of weeks, then charged the battery and started the car up and gave it to a mechanic who I could trust: they have checked the wiring and everything looks ok, AND the alternator does not have that burning smell anymore! The voltage is now 12.5V at idle, and when pressing the throttle it goes up to 14V once off the pedal goes back to 12-12.5V. This has baffled everyone - how can a burning alternator suddenly be charging the car at WOT, and why does it drop down to 12-12.5V if not on WOT? Not to mention there has been no battery/alternator warning message on the dash at any point during this alternator feast.

Anyways, the mechanic has told me they have cleaned the earth connections, and wants me to take the car back and test drive it for a short while to see what happens. It seems like this is an intermittent issue that destroys alternators when it happens but cannot be traced likely because of its intermittency. The phantom alternator #3 being able to charge the car again at WOT makes no sense either (the burning smell is indeed gone and it was pretty bad and noticeable earlier).

I will report back once I test drive it around.

The only other major gripe I have about the car is the suspension is very stiff (because of the ESP malfunction error message). Star tells me SAS is defective, so may change that at some point.

Thanks all!

e55aed

If you don't mind me asking, what was the original electrical issue that was fixed?

e55aed

Belt checked by mechanic, tension and condition were fine.

e55aed

Believe me I would do that if it were financially feasible. The dealer here says they will charge me $4,300 just to register it in their system before looking at it since my car is an import. Honestly thinking of writing a letter to MB HQ about this....

Been measuring for a month now, let's see (above update post). Next money pit will be buying a BCM if issue persists (since battery, wiring, all look fine, however if issue is intermittent I am looking for a needle in a haystack in the wiring...).

chassis

The electrical system is modified.

Alternators are eaten.

Battery needed to be recharged.

Star showed no “major” issues.

Replace the battery and tell us all of the codes that were found by Star, especially the “not major” ones.

MartinWake

Yeah I think the battery could be the cause... Mine ate a couple alternators as you can see on my previous post so now every once in a while ill throw the battery on a charger just in case...

The part number stuff I also saw when switching my alternators some are original MB and some are still oem Bosch but not original

Also I used to check the volts with the obd app but that shows the volts to the obd port so I would suggest checking the volts on the dash with that secret menu or whatever I have a cl55 so I can hold down the rest button on my ac and shows voltage there too...

its always at 13.8-14v on there and on the obd port app its a little less.

https://www.mercedesmedic.com/ac-w22...ng-fault-code/

e55aed

Not for me. Battery is brand new (installed in August 2020). Auxiliary battery is old but is also fine (in any case it is not connected to main circuit unless triggered).

Let's see. I will get the car back today and find out.

What was the original electrical issue on your CL55?

e55aed

Battery already replaced in August 2020 with brand new Bosch AGM unit.

Electrical system unmodified (except for the head unit)

I'll share a star dump once car is back

Battery (brand new) only needed to be recharged since alternator was not charging it (it holds a charge with no issue once charged).