The problem that is bugging me now is on my 82 240D with 242k miles. You can't see it during the day but at night even with the headlights off you can very plainly see the battery light lightly glowing. It does seem to pulsate or flicker ever so slightly if I stare at it. The oil pressure gauge is leaking but that should cause this problem (I am planning on hooking up an aftermarket oil gauge so I don't have to keep cleaning up the oil behind the dash).
I have read other posts that maybe suggest to check the regulator or the alternator. Any other thoughts?

Erik

Yes, check the voltage from the alternator either with a multimeter at the battery or just buy a voltmeter that plugs into the cigarette lighter.
I'd check the fitting at the oil pressure gauge. If the problem was the gauge itself and not just a loose fitting, I'd pick up a set of instruments at the junkyard before putting in an aftermarket gauge.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

by any chance is there a squeeking coming from the front of the car? you could simply have a loose belt. usually the regulator goes until it quits... never brings on the light... worth a check though. pull it and inspect the brush length. a loose belt could cut alt output. a bad regulator could cause the light... it's just not common.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Voltage regulator brushes. Get worn down to nubs, don't make good contact, get hot and begin to groove the copper commutator surfaces.

Easy change. Do a search for explicit instructions, but in general a couple of screws on the back of the alternator, an electrical plug with a spring clip, and an external ground connection with a capacitor, I believe, also held on by a screw. Roll the old one out and examine it. One short and one significantly longer brush is a sign of a bad diode, a rebuild is in order by someone who does a real rebuilding job. Deep grooves in the wear surface is a sign the commutator bars are also grooved. Leads to rapid wear of the next set of brushes and if you rebuild, this surface can normally be polished if there is not a serious taper due to bad bearings and alignment, etc. Some here have found sources for the brushes and just replace the brushes. Costs less, that is for sure.

But, by all means check the belt tension as that is also a potential problem, and is entirely unrelated to the voltage regulator (which has the brushes on it).

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)

possible alternator or voltage regulator problem. On my car, the battery light was very dim also before changing to a new alternator. Check the voltage of the battery when the light is dim, that should help diagnose the problem a bit.

__________________
1983 300 Turbo-"Nora"
1983 240D Auto "Lucia"-slowest on earth-1st love
1985 300 Turbo-Blue Goose-slowly plucking parts

http://i117.photobucket.com/albums/o...ly15/mbsig.jpg

A dimly lit battery light is usually a failed diode in the alternator. It will charge, but never to full capacity. Cannt hurt to inspect the regulator and/or brushes tho.

__________________
81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

I had the exact same problem on a car (not Mercedes) with the same type of Bosch alternator/ regulator/ light setup as the Mercedes. I tried everything including replacing the good alternator with another good one but the battery light was still dimly lit at night. Drove me nuts! I finally found the cause. It was a loose starter motor solenoid bolt for the battery + cable at the solenoid. Tightening it fixed it.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I like that car brown rice, Ig uess its name is Lucia, but it looks nice!!

My glowing light was the alternator brushes wearing out on my 240d 80. They finally went totally, bright light. I bought a regulator/brush set, total waste of money. Because of the grooves cut in the copper ring on the armature, the new brush set lasted 300 miles. If you're inclined to spend the time on a brush set, take the old set off and look at the armature with a mirror and flashlight before you buy a set. If there are grooves in the rings, exchange the alternator. If your time is valuable, turn on all accessories, measure battery voltage idling, if low and belt not loose, (my new one does 12.5 idling, 13.5 running) exchange alternator.

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'80 240D biege "Mercey Bird"
'80 240D light blue "Slug"
'80 300SD dark blue "Theodin"

I agree with IndianaJo, and the damage to the commutation bars is made more severe by driving longer with the light lit dimly. The alternator tries to produce the voltage needed, however, the brushes impose an increased voltage drop when they don't contact the copper bars on the shaft consistently. This leads to heating and arcing. Which the copper doesn't tolerate well. The longer you run with a dimly lit warning light the more likely you are into a complete rebuild or exchanged alternator.

If this is the first alternator in 200,000 plus miles you might consider a new/rebuilt one anyway. Bearings, diodes, winding insulation, condition of commutator bars.....all kinds of parts may be worn to their limits by now.

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)