i just recently cleaned them and cleaned up the ground point for the batt..i did this when i cleaned out my battery tray and sprayed it down with some rust enamel. that was in june im thinking.

I dunno where you're at (I'm in So.Cal.) but Harbor Freight has stores all across America (is this a great country er whut ?) PLUS online ordering .

I'm still using a 35 year old Radio Shack cheapo analog meter when I'm in a hurry , I vastly prefer using good SUN test equipt. or my Bekmann meter but you _MUST_ use an analog meter when trouble shooting starters and doing load tests and the fancy-schmancy digital ones go all wonky under load and stop working altogether if the votage drops below 10 volts...

Try to turn the alternator fan by hand ~ it should be tough to rotate , if it's easy it's time to re-adjust the fan belt.... I hadda do mine on my old '79 300CD to-day as I was doing routne oil change and fuel system mtce., I changed the alt. (55 A unit) and belt in Pecos , Tx. a week and 3,500 miles ago...

A tiny bit of belt slip will cause serious low charging .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

If the ground for your light is corroded or broke your light won't work, but power will still read 12v if your tester was grouded elsewhere.

did you spray the body were the ground conects if so thats stuff "rust enamel" may not be a good conductor

__________________
Jason Green
1977 240D AUTOMATIC the Beast
1974 Super Beetle



Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself.
- Mark Twain, a Biography

I had the same prob after installing my amp/sub. took the battery out and load tested fine. I installed a powercap and havent had a prob since. I don't know If I actually solved the prob but from what I understand the mercedes vehicles are particular about power management.

__________________
Owen

87 300TD 603 I-6
94 Jeep XJ I-6 4.0 (see the pattern)
89 750il
seventy-two hundred feet above sea level (kinda cold up here)

i didnt spray the ground area with anything..i cleaned off the paint with sandpaper and mounted it....ive had my subs since january..this is the first battery drain issue ive had...even when they wernt connected something still drained the crap outta my battery....

test results...

--i tested the underdoor light to make sure it was turning off when the door was closed...volts dropped to 0...that isnt causing the problem.

--i tried to start the car (this morning) it tried to start but couldnt muster the energy to crank it enough...

volts @ battery (after sitting all night) 11.73 VDC

--50amp Starter/Charger connected to battery. I''ve removed the fuse to my amps/subs in the trunk for the remainder of these tests

volts @ battery - 13.94VDC
Battery appears to be completely drained had to wait ~5 minutes before it would start

--engine started
battery volts @ idle (550-600rpm) - 13.74VDC
battey volts when engine revved max - 13.85 VDC

i let the engine run for a little bit (10min) then retested.

battery volts @ idle - 13.74
battery volts @ ~2200 - 13.85 (engine was 60C)

--turned engine off. restarted.

Inserted Key and put to RUN. Volts dropped to 11.50VDC
Started Engine................... Volts dropped to 10.50VDC
Engine running....................Volts slowly climbed to 13.73VDC

--turned off car..observed voltmeter..
Volts - fell quickly to 12.59VDC then slowly to 12.48VDC

--attempted restart 10m later
Volts b4 start - 12.35VDC
Volts when key on - 11.4VDC
Volts when cranking - 10.4VDC
Volts when running - slow climb to 13.74

I checked the alternator belt..it was rought to turn..it had just been adjusted not too long ago

I am going to take my car down to Advance and have them do their tests on it see what they determine...

anyone interpret my results?

how i checked my volts all those times..lol



Thanks

Kris

I took the car down to Advance Autoparts to test it. The battery checked out GOOD, but had a low charge.

The alternator, when tested, put out .03 Amps.

I am getting a new alternator. But I need to DOUBLE check that the AL129X Alt is compatible with the 617 (300SD)

can anyone verify this one for me?

By what you posted, your alternator seems to be working fine.

I think there is a draw on the system somewhere that is sucking it down over long periods of time.

Trunk light?
Loose wires?

Your meter is just like mine...I believe it has a amperage setting where you can read the load.

Hook it up like this:

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