1989 300ce charging issue battery dying ,stalling

[mlozzi200478]

my car battery died i jump started it,it died again i had the baterry tested it came back as defective,i replaced the battery,it was still only putting out about 12.85 volts then with the headlights and heater blower on battery died,i replaced the external voltage regulator,assuring this would fix the issue,i drove the car with the headlights on and the blower motor sure enough the battery died,im clueless now,its got a new battery and external voltage regulator.i drove the car for 30 mins then let it idle with nothing on for 15 mins,i then drove off with the headlights on and blower motor for heater the engine of course stalled on me,im lost i have a new battery and voltage regulator,there is so many wire leads under the hood mostly near the battery,is there something im missing along the line that is causing a non charging condition.is it possible that the internal components in the alternator may have something to do with it.what am i missing should i check all the wire leads down to the starter to make sure there tight,what else is involved in this charging system,please any help will be greatly appreciated,im so lost,mercees charging systems are nothing like general motors.i need allot of help anyone please give me your input,please.marc

[lee polowczuk]

all it can be is one defective diode in the alternator....and that will cause a problem

i think that 21 years....and probably 175-225k miles is about all you can get out of an alternator....

i replaced one this year in a 1989....and two years ago in a 1988....

both died with 200k plus miles on them..... and yes...i tried the voltage regulator trick..

[mbzman]

Have you cleaned the battery cables and terminals? As a last resort you could go around and try cleaning all of the grounds up. With that said, if the battery and regulator are new and the car is still dying then really there is only the alternator left. These alternators were pretty weak when new, especially when you consider the amount of electric features these cars come equipped with. If you are planning to upgrade the headlights or stereo system in the future, I highly recommend that you upgrade to a more powerful unit.

[mlozzi200478]

well,i never knew a diode in the alternator could do this,yes all the terminal ends are clean,they even are covered in dielectric silicone.your right the only other part left in the charging system is an alternator,i thought for sure the regulator would fix the issue,its funny it almost seemed to last longer with the old regulator,maybe its my imagination.as far as i know this is the original alternator from 1989,there is no loud bearing sounds coming from the alt..yes its only 80 amps,thats crazy when you consider everything is power on these cars.the car has 68k original miles,but i think i will look into a remanufactured alt,autozone has one with the regulator installed for $160.00.i willjust swap out the voltage regulators and return the new on ine the alternator,any other hints or ideas would be very helpfull,thanks.marc,is this a crazy idea but could i drive it up on ramps and check the connectors on the starter,to make sure there tight and not loose,causing a bad charging condition.please help!!!!

[mbzman]

I believe it is actually only 70 amps. This is what I have in my '89 300CE and I would think you would have the same unit, unless yours has been changed before. Some people have upgraded to a 143 amp unit from a late 90s SL or S-Class. This is something that I will probably be doing in the near future. A good used unit can be had for relatively cheap ($100-150) and modified for the M103. If you do a search you will find more info on the swap.

[mlozzi200478]

thanks for the input,i think id like to upgrade to the 143 amp alt,mercedes was not compensating enough when they put in a weak 70 amp,i mean everything is all power what the heck were the engineers thinking,ive read of allot of people doing the swap,i think i need to change the pulley on the new one right? so the serpentine belt lines up,boy it would be great to have a higher output on my alternator,id have no worries about the charging system failing on me,i will look into swapping out the alternator,is ebay a good placde to find one of these alternators? where would you recomend purchasing one,maybe a junk yard?,thanks.

[mak]

my 300se 89iode connections on two diode were bad
mak

[mlozzi200478]

does anyone know how to loosen up the serpentine belt tensioner,im not familiar with the german setup.i need to replace the alternator,the serpentine belt looks like its the hardest part of it.i see a threaded stud sticking up near the center of the engine near power steering pump,is this what i need to mess with to loose up the belt?thanks.marc