1991 300e voltage regulator - PeachParts Mercedes-Benz Forum

lebstyle · #1 07-12-2007, 04:31 PM

hi, today while i was driving on the highway, my lights in the dash started coming on, then all the power stuff in the car started shutting off, then slowly the car loses power, then it turns off. i boosted it a few times till i could get back home by a friend. it didnt seem like it was charging.
but when it stops, there is still power in the battery, it doesnt completely die, but not enough to start the car.
i took the voltage regulator out, and one end is bigger than the other. they both are spring operated, one is pretty short, and one is a few centimeters longer.
could thing be the problem, or should i build the whole alternator.
b/c a couple of weeks ago i was on the highway and the same thing hapenned, but then it would kick back in while i was driving, so it never completely died on me. and for the last 2 weeks it was find in the city till the other day i forgot the lights on and the battery died, then i got this problem again.
here is a picture of my voltage regulator.

david s poole · #2 07-12-2007, 04:39 PM

i would replace the complete alternator unless you know that it was recently replaced.

saumil · #3 07-12-2007, 05:37 PM

Did you charge a dead battery with an external charger before connecting the battery terminals OR did you charge the battery by running the car ? If it was the later, that could explain problems in your alternator, must be a very old alternator. You can either buy a new one as David suggested or get yours rebuilt, dont just replace the regulator.

RAYMOND485 · #4 07-12-2007, 05:59 PM

1984 300d Turbo
Replace The Battery And Alternator

lebstyle · #5 07-12-2007, 06:20 PM

i am getting the alternator rebuilt tomorrow, they said it will be about $150 if i take it to them off the car. the battery is fairly new.
and yes i did charge the dead battery by running the car, but it was jumped by my other car in the process, b/c it turned off when i would take the cables off.
but when i let it charge off my other car for 20 mins, it stayed on for a while after, and started normally before i went on the highway.
thanks for the help.

las769 · #6 07-12-2007, 06:34 PM

They should be the same length mine wore down and stopped charging
i replaced it with a unit i found for 18.00 everything works great again

lebstyle · #7 07-12-2007, 07:16 PM

what does it mean when one feather is shorter than the other in my case?
something wrong inside the alternator?

Mike Murrell · #8 07-12-2007, 08:11 PM

Quote:

Originally Posted by lebstyle

what does it mean when one feather is shorter than the other in my case?
something wrong inside the alternator?

Good question. Both of these carbon bridges(as I call them) are spring loaded. Maybe the one that's worn down more was stuck and didn't retract as intended, thereby wearing it down.

Brand new, out of the box, they are 1/2 inch long each.

I recently had an off-the car-Asian alternator rebuilt for 1/2 what's shown above by an established local elect. rebuild shop. I know I'm not comparing apples to apples and you may be in Northern Calif where everything is big $$$. Just throwing out my 2 cents.

saumil · #9 07-12-2007, 09:46 PM

Also when you put the alternator back, make sure your battery is fully charged. And also never disconnect the battery cables when the car is running (a trick we used to apply to see if the alternator is working or not) would damage the alternator again. And I agree with Mike, $150 seems excessive, you may be able to find a new one for close to that price.

lebstyle · #10 07-12-2007, 11:03 PM

does the new one come with the voltage regulator?
or do i buy that separately?

Mike Murrell · #11 07-12-2007, 11:31 PM

I'm not sure if you would actually be able to get a "new" alternator. Most for that era would be remanufactured. I would look for a Bosch reman and yes, they do come with a new volt. reg.

saumil · #12 07-12-2007, 11:37 PM

As far as I know, it is complete and ready to go, some come without the regulator but most have the regulator on. Thats correct, not a brand new, I am sorry, I meant a rebuilt one but something you can buy from any local auto store with a lifetime warranty.