While driving in traffic on Sunday I noticed all of my dash warning lights were flickering at idle. Just tested my alternator and didn't get a jump in voltage after I started the car. Was still around 12.5 volts. I swapped out my voltage regulator about 2000 miles ago so I'm guessing it's alternator time.

Just in case it isn't, is there any sneaky bulb or fuse that could prevent the battery from charging? I ask because this was a trick on my 1980 BMW 528i. If the battery warning bulb was disconnected or burnt out your battery wouldn't charge.

Will go ahead and order the alternator but is there anything else I should look for that would prevent the battery from charging?

The battery bulb in the dash can cause the issue, however the flickering lights are part of a backup scheme to allow the alternator to flash in the event of an alternator bulb failure. Likely the new regulator is bad (new doesn't always mean good), or the alternator is failing (probably worn slip rings).

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Many new voltage regulators of aftermarket suppliers where junk. Forcing us to buy the more expensive original brand type in my opinion.


Typically as in your case having very short lifespans in my past experience. No certainty that this is your issue but could be. Stay away from aftermarket starter and alternator parts made by marginal Chinese suppliers.


In my opinion they have done massive damage to the rebuilding of alternator and starters business. At the same time they probably build for the big names today the original replacements but with quality build standards.

I used the Bosch voltage regulator thinking it was OE quality. The KAE regulator I replaced was causing my radio to cut out and also burned out my brake light bulbs. When I checked the voltage it was over 18 volts on the old regulator.

I've ordered the Bosch alternator so hopefully that solves the issue.

I would stick to the official Bosch factory reman alternators, not the generic ones from the chain auto parts store. A little more expensive but worth it.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I ended up buying a kit from these people Rebuilder in a box for my Dodge Cummins. Perhaps the vids will be useful and/or they may have parts for the MBZ.

The new Bosch voltage regulator was bad out of the box on my SD but I eventually found a good one. I forget whether the unregulated alternator puts out a high voltage but remember that something I found when testing indicated that the voltage regulator was at fault. Also, make sure that the glow isn't stuck on as that can pull the nominal alternator voltage down. The parts store condemned my regulator when the car was glowing. You have to be certain what your test results mean or will install incorrect parts.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

While i'm not a 190D expert, this guy on Ebay sells beefed up stock alternators. Maybe he has something or can help you out. As i remember, you can actually call him and ask tech questions. Wanting OEM fitment, i bought one of his 300d units and it hasn't missed a beat in the last 10k mi.

https://www.ebay.com/itm/MERCEDES-ALTERNATOR-240D-450SL-74-77-78-79-1980-81-83-85-120AMP-Diesel-Generato/362637532764?hash=item546ee19e5c:g:TdsAAOSwuMFUi6jq:sc:USPSPriorityMailLargeFlatRateBox!94133!US!-1

Pretty far from stock considering it has ground down case lugs and a totally different plug system from the stock "push pin" style connector. That's just a later alternator sold to people who don't know better for a silly amount of money. I picked up the 143A version of that alternator a few months ago for $30 shipped to my house and running perfectly in my 350SD.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

What's the best way to determine whether my glow plugs are staying on? Can I unplug the relay and still start the engine to check voltage?

My battery was pretty low yesterday when I got home, charger indicated about 25 percent and it took a long time to come up. Fully charged now. Battery is less than a year old.

PKdavidson, on a cold engine if leave the key in the glow position, you should hear the glow plug relay click off after 10 or 15 ish seconds.

Open your hood, put in glow position and walk over to the glow plug relay for a listen.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Get one of those led voltmeters that plugs into the lighter socket. The glow system pulls so much current that system voltage will be below 12v while they’re heating.

Just checked the glow plug relay. Heard a loud audible click after about 10-15 seconds. Sounds like the relay is working fine and the glow plugs are off. New Bosch remanufactured alternator gets delivered this weekend.

UPDATE:

Finally had a chance to swap out the alternator. What an easy job. Think I did the whole thing in less than 40 minutes. Light flickering is gone and the battery is charging again. I think I found my culprit: the new voltage regulator.

Looks like the voltage regulator was subjected to poor installation (my fault, was in a huge hurry originally due to family emergency). And also the channels on the old alternator were worn down to nothing. All good now!

Well, I spoke too soon. Battery isn't charging even with new voltage regulator and alternator. Just had to get a jump.

Any other ideas? Would the OVP prevent the car from charging?

Now you have to check carefully. New alternator may be bad. Many problems with rebuilts today. I do not know if the practice has changed. Basically most chain stores sold rebuilts with junk aftermarket parts used in rebuilding. Possible a junk brand of voltage regulator on it has failed.


First of all check for tension on the belt. Although unlikely if it is serpentine. I have never owned a 190d.