1992 w124 300D. Battery light and other dash warning lights sometimes dim. If I rev it "good" the lights will go out and stay that way until I rev it good again. When it does glow dim I can actually hear a slight whine that varies with engine speed. When the dash warning lights are not doing the dim glow thing....there is no more whine. I suspect regulator. Anyone know if Ican change it without removing all kinds of other engine components?

I don't have/know about 124 but you can on 126 500sec, 300sd, & 190 2.3 without removing anything.

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K

regulator should be same as older vehicles. my 93 is, as is my 87
if the alt has external fan, near the belt, then the regulator should be replaceable...
however, I've never seen a bad regulator cause a light on the dash... slipping belt, or bad alt, sure, but the regulator usually just lets the battery die.

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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 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Thanks guys. The thing on my mind is that I can make the problem appear or disappear (the majority of the time anyway) just by accelerating hard. If I hit 3500 or more rpm the dash lights begin to glow at idle ..... They go out as soon as you ease it up to reach 1000 rpm. Then if I accelerate again and exceed 3500 rpm, the battery/dash lights go out and stay out. They don't come on at idle. It seems once I hit some good rpms that is when the lights start glowing or stop glowing at idle. Given that..... I was thinking the regulator is not stable.

There may be something wrong with the alternator itself. However, checking the voltage regulator first is a good idea. Also, check the electrical connections and grounds to make sure they are good.

Bad battery will not cause the symptom you are seeing.

Usually, it's an imbalance in the charging systems in the alternator. There are multiple charging circuits and they are not putting out the same voltage - allowing current to flow thru the bulb.

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Codifex
1981 240D ChinaBlue (Got her running with a donor engine.)
1983 300DTurbo w/sunroof.
1984 300TD manual sunroof. (Electrical Gremlins)

didjafixityet?

I'm thinking the diode pack is failing... I bet a multimeter will register high a/c voltage...

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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 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

It's not fixed yet. I have had a multimeter on the battery in the past. Seemed it was a little low when the light was glowing (in the high 12 V range). When not glowing it was over 13 (don't recall exact number). The other thing is that the other warning lights on the dash also glow dimly when this condition is present. Makes me wonder too about a ground being less than par.

AND, the whining noise in the engine bay (i.e. alternator straining?) is there too when they are glowing dimly. Appreciate any other ideas/advice. But it seems it's time to deal with testing the alternator...which by the way was purchased new about 2.5 years ago and it did this every winter. I would just keep my rpms below 3000 and the lights would never glow dimly. In summer I think it was pretty much a non-issue. Now it's just time to fix it I think.

My "generator" light flickers and gets dim too (in '71 220D) at times, and different rpms and speeds have an effect on it. My belt on the alternator squeals sometimes. I am not sure if this flickering is related to the weak idle issues I am having, or the occasional alternator belt squeal. When it does squeal, I just have to punch the accelerator and get it up into the next gear, and it'll stop for a while. It's odd...

Kwoody and possibly the OP-
Flickering of the "generator" light on my 220D is caused by a bad connection between the alternator and the alternator plug. If I take it off, clean all the connectors, crimp the female connectors a little, and put it back together, the flickering stops. But so far, it seems to start back up again a few months later. So that is an easy (if not permanent) fix to try. I bought some connector grease that is intended for aluminum wiring in homes, and I hope to try that out soon. It should keep corrosion and dirt from affecting the connection. I have a similar problem with my right turn signal. It stops working (like a blown bulb), but if I clean the connectors, it starts working again. I think there must just be some corrosion/dirt build up in the connectors on these old cars (or at least on mine).

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Update: I will let you know. I dropped the car off at my expert mechanic for some services and he's planning on performing diagnostics on the alternator too. When he has the bottom pan/shields off the car for my transmission service he is also going to inspect the ground connections/straps for the car to be sure they are sound and clean. I could do that but I don't have a car lift and since he has it for other purposes it makes sense for him to check it all out. Besides its 25F outside and my driveway is cold enough that I don't want to crawl under there except for oil changes in the winter time. Thanks.

Resolution: The alternator was faulty. The tests revealed a maximum output of 30 amps under load. So far the dim lights on the dashboard are not glowing. So, it looks like my mechanic solved the problem. Thanks for all the help.