Hello

I have a 1983 MB W126 300SD 421k km.
5 weeks ago i took the beast to the car wash, i wass the only guy in the car wash so the boys did a very good job, so it took around 20 minutes, it was very humid inside
I tryed to start the car no luck, got boosted car started fine, got home the car didn't start however if i boosted it was starting ( i drove it for one hour, shut down the car try to restarted no luck).
So i decide that it was my batery, changed for a new one, everything was fine.

yesterday it was snowing/raining and humid got to my friend house and the car wasn't starting, i boosted the car and she started, drove it for about 30 minute got home shut down the car, try to restart the car wouldn't start..

Where should i start looking ?
My alternator ? ( i do have the little batery light on my dash sometimes is on sometimes is off when i'm accelerating the light is off)

But if my alternator wasn't working my battery wouldn't last for 5 weeks of starting/driving...
My batery is new so i will take it out of the equation.


Any suggestion ideas are welcomed

Perhaps your alternator isn't putting out full output. Only bringing battery to 50% or so.
I am assuming when you changed your battery you cleaned the contacts real good.
Check your grounds where ever they attach to the chassis and engine.

__________________
1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

I cleaned the 2 connectors on the battery.
2 questions
how do i test my alternator charging capacity ?
where is the grond attached to the chassis ? that might be the weakest link

You could load test your battery with a load tester. If it test good then I would look for a ground issue. I don't know where the ground straps are are on the MB, I've had other cars with similar issues. If your battery tests bad then it would point towards the alternator. Also look at the conections on your starter to see if there is any corrosion.

__________________
1959 Gravely LI, 1963 Gravely L8, 1973 Gravely C12
1982 380SL
1978 450 SEL 6.9 euro restoration at 63% and climbing
1987 300 D
2005 CDI European Delivery
2006 CDI Handed down to daughter
2007 GL CDI. Wifes

Sorin,

Sounds like your alternator brushes are worn. These can be replaced individually if you are very frugal and find just the brushes from a source, or you can buy a new voltage regulator, which comes with the brushes. In any case you have to remove the old voltage regulator, which is on the back side of the alternator. There is a spring clip that holds the electrical connection down (a plug connector) and then two screws that fasten down the ears of the voltage regulator flange. There should also be a noise suppressor connection to ground on the case of the alternator that may be in your way. The old alternator kind of rolls out and the new one rolls in. The new one will be a little harder to get in than the old one was to get out, mainly because the brushes are several cm long on a new one, and they must be pushed into their housings against a spring load as you roll the voltage regulator to insert it. The red light should never come on with the engine running, and it is feasible that at higher engine speeds you actually make enough voltage with worn brushes to make the light go out. Also, Diesels don't use that much electricity when running except if the headlights are on, so the battery charge can last quite a while. Good luck and I hope this helps. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Thanks for the quick reply and good explanation

the red battery light is there since i bought the car this June i will buy the voltage regulator and get rid of the little batery light.

Sorin,

Easy alternator test is a voltage check. You should read about 14.5 volts when the engine is running high idle or faster.

P E H

I would suggest that the alternator voltage should be between 13.6V and 14.0V on a fully charged battery depending on load and engine speed.
As the alternator charges (from a cold start) the voltage may reach up to 15.0V, but should never exceed that voltage for more than a second or two at the most. The voltage should then drop back to the 13.6 - 14.0V range.

An alternator which consistently has an output of 14.5V after recharging the battery will "cook" the battery.

Please remember that the battery is important to the alternator, to moderate the output and allow the regulator to operate correctly. DO NOT OPERATE THE ENGINE UNLESS THE BATTERY IS CONNECTED. The alternator and most other electronic devices in the vehicle WILL BE DAMAGED.

__________________
Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

Just to make sure how do i mesure the output of my alternator ?
at the batery?
or at the alternator ?