Would a bad/shorted cell in the battery cause an alternator to keep going out. I have had mine rebuilt twice now...the inside of the alternator is getting so hot it is melting the rectifier and stuff. I have not tested the battery yet...but some fellas at work are pretty convinced the battery is the bad egg...any ideas???
Jason

 

Suggest: maybe a bad battery, but most good quality batteries such as MB or other top brand batteries do not just short out in the years of 2005+. Best to also check the wiring to the alternator and check the main alternator wiring tracing back around the exhaust, then recheck all connections at the battery and if applicable (did not check your profile for year/type of car) , any over voltage relay, etc.

 

its an 88 190e...battery is in front. Thanks for reply though!
jason

 

Think my reply will be as to ask more questions than provide any answers!
Have never heard of, or had personal experience with bat short causing alt damage. But you never know with elect.
First of all, I hate electrical problems as the resolve is usually quite simple-when you find the answer. Could the alt possibl melted internally from an "overload" such as demand from alt being higher than its ability to output? That would point to regulator (but is that not internal on MB alt)? If so, that shoulda/woulda have been replaced 2 x during rebuilds. If not, (if external , has it been replaced? Check the demand of regulator. Could there posibility of an incorrect "wiring" to/from alt exist?
Most folks do not realize that "ground" is other half of curcit, and an inconsistancy (loose connection) can confuse system and give it fits.
On that note, do recall personal experience cooking bat < 200 miles less than 4 hours after leaving ground conection little loose (on a mutiple bat vehicle). Only noticed when smelled bat acid in engine compartment. Raised hood to smoking bat! And chose to leave it alone till cooled down as they are quite volitile at this stage.
The above paragraph does somewhat in reverse, state what is occuring to your vehicle.
So, see, did not answer, but gave you more to think about.

Ever notice that the "electrical" guy in the repair shop has little hair?
As always, no warranty is implied or expressed.
Tom

 

I got the battery tested..it is OK

I will try to expalin what originally happened.
I bought this 1988 190e about 1.5 yrs ago. Bought it for a daily driver to get to work and such. Love the car...When I bought it it had a couple problems like some of the windows wouldn't roll up and stuff...but nothing I couldn't live without.
About 12 months into owning it, it was fine and dandy, I drove it to work like normal. After the work day, I went to start it and nothing...no power (I didn't notice anything out of sorts on the drive in) I got a jump and as soon as I removed the cables (...it died...so thst kind of told me it was the alternator). I got it trailered home and had the alternator rebuilt by a guy who does this for a living. At the time of pick up, he said he has never seen an alternator "melt" on the inside like this one. He said that the output is too great for alternator to keep up with. So, thinking it was a fluke..I reinstalled the rebuilt unit and went on my way. Upon installation, I checked the output of the alternator with car running...was in the high 13VDC, thought that was normal...It drove fine for the first few days...then I noticed the the headlights acting funny...so, carrying my meter, I pulled over and with car running...was only measuring 10.5 VDC not good. I got to work...barely...and the same thing...has to jump to start and rebuilt again. I talked to a mechanic buddy of mine and he said run a ground from the battery to the chassis of the alternator so it has a definite ground...did that and reinstalled. Upon restart...output was high 13VDC...good!...but a few days later...less than 100 miles...same thing...alternatorout again...and this is where I sit...I haven't had it rebuilt yet.

Basically, this problem happened overnight....seemingly by itself!!

Another note...The car has been sitting since November, and even though the battery does not have enough juice to turn the car over, the door buzzer still comes on when you open the door...tells me there is not short when the ignition is off.

I AM AT A LOSS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!

Where is the regulator on this car????

Thanks
Jason

 

Something is wrong. You shouldn't get repeat failures.

Alternator should be putting out about 14v under load and NEVER going below 12.5v.
Could be the battery but not at the top of the list.
Need more FACTUAL info to determine what is wrong.
PM me with your data and I will advise.
eg. Mileage. Battery age, problem start date. Who's done what to the system. More detail regarding "Melted" please. Photos?
Not rocket science.
Alternators do not like "jump starts". Don't suppose you have jump started it for some reason?

Stuart

 

Some more musings here.
From your last email Hoytheld, the description you give does seem to indicate the problem would lie between the output side of alternator, back to the battery. Such as a floating short (intermittent to ground)on the output side of aLT.
OR, again, some source(intermittently it would appear)demanding extreme load until failure. Bosch disclaims their alts life will be "greatly reduced" if battary is not FULLY CHARGED charged prior to installing alt! (ie,higher demand than ability to output).
The 10.5 voltage would seem to bolster the "short to ground" theory, OR driving with load on (ie, lights on for period of time (after alt quit)before you were able to stop and check voltage.
FYI
I have personally experienced internal (solid state )regulator failure and glow plug controller (SS) failure (dif occurances, dif vehicles)from thinking I could get away with Mig welding closeby vheicle. These failures were not on MB, but principles are same.
Have also experienced "bleed over" from one circuit to another by worn/thin barrier. However, with load you are describing, do not think this to be issue.
I am not yet familiar enough with MB to know where reg is located, but most velicles made in last 20 years or so, have placed them inside/or fitted directly/as a part of the alternator. Most of the Bosch, Motorola regulators are on the back, about the size of a double book of matches, and chould have wiring directly attached. Again, this shold have been changed out on rebuilt-but attempting to address your question.
And yes, do agree with snanceki, regulators, especially solid state, do not like surges or external fluxuation in current. But sometimes it can't be helped.
Tom
Losing any hair yet?

 

LOL! Not losing hair yet..still have an extra ride for the time being!


I have no idea what is wrong...Both times I did not recharge the battery before The install of the rebuilt unit..I did jump to get started..then relied on the alternator to recharge the battery. I am about to the point on letting my mechanic pal look at it to see if he can figure it out...he has experience with this particular car...he has worked on it before when the previous owner (buddy of mine as well) had it.

Would changing out the 3 prong plug/wiring harness on the alternator help? (plug that send wires up to battery and that distribution block, 3 wires I think)

Thanks for all the help
Jason

 

Suspect you may have identified the cause.

......."Both times I did not recharge the battery before The install of the rebuilt unit..I did jump to get started..then relied on the alternator to recharge the battery. "

Alternators do not like charging a "flat" battery especially if it is flat if it has an internal fault since alternator load is determined by voltage feedback from the battery.

Can't be of much more help I'M AFRAID.

STUART

 

I guess I could give it another go to root out the cause of a dead battery...its only $60 to get it rebuilt....
I spose I'll try it