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  #1  
Old 09-15-2013, 01:26 PM
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Unhappy Flickering/pulsing lights

Hi folks,

Like the title says, on my 83 300D I have (mildly) but noticeable flickering instrument cluster lights while driving at night that started out of the blue about three nights ago. Basically here is what happens. After running for a few minutes, I noticed the white instrument cluster lights will start to lightly flicker while running down the road.
Last night when I noticed it, I stopped in a very dark area and here is what I observed. The instrument cluster dash lights and headlights will flicker/pulse rythmically at a rate of about 2 times per second. They will flicker at idle or if the engine is revved but it is more noticeable with the high beams on or at idle. The interior lights (if turned on) will mildly flicker as well

The battery warning light does not ever come on when this happens but the battery warning light does come on when you first turn the key on so that is acting normally.

What do you think.....voltage regulator going bad, alternator going bad, or something else? I'll check the battery voltage and the alternator for charging voltage in a little bit, but outside of that what do you suggest.

Thanks in advance,

Glenn

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2012 Mercedes ML350 Bluetec 59K (hers)
2002 VW Jetta TDI 210K (mine)
1998 Volvo S70 T5 Turbo 161K (kids)
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1983 Mercedes 300D 350K (diesel commuter)
1965 Corvair Corsa 98K (fun car)
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  #2  
Old 09-15-2013, 01:37 PM
300D-91's Avatar
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Quote:
Originally Posted by psaboic View Post
Hi folks,

Like the title says, on my 83 300D I have (mildly) but noticeable flickering instrument cluster lights while driving at night that started out of the blue about three nights ago. Basically here is what happens. After running for a few minutes, I noticed the white instrument cluster lights will start to lightly flicker while running down the road.
Last night when I noticed it, I stopped in a very dark area and here is what I observed. The instrument cluster dash lights and headlights will flicker/pulse rythmically at a rate of about 2 times per second. They will flicker at idle or if the engine is revved but it is more noticeable with the high beams on or at idle. The interior lights (if turned on) will mildly flicker as well

The battery warning light does not ever come on when this happens but the battery warning light does come on when you first turn the key on so that is acting normally.

What do you think.....voltage regulator going bad, alternator going bad, or something else? I'll check the battery voltage and the alternator for charging voltage in a little bit, but outside of that what do you suggest.

Thanks in advance,

Glenn
Sounds like its alternator / regulator related. If your meter doesn't turn up anything consider taking the alternator to a car parts store for a free check.
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  #3  
Old 09-15-2013, 01:51 PM
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Answer

Quote:
Originally Posted by psaboic View Post
Hi folks,

Like the title says, on my 83 300D I have (mildly) but noticeable flickering instrument cluster lights while driving at night that started out of the blue about three nights ago. Basically here is what happens. After running for a few minutes, I noticed the white instrument cluster lights will start to lightly flicker while running down the road.
Last night when I noticed it, I stopped in a very dark area and here is what I observed. The instrument cluster dash lights and headlights will flicker/pulse rythmically at a rate of about 2 times per second. They will flicker at idle or if the engine is revved but it is more noticeable with the high beams on or at idle. The interior lights (if turned on) will mildly flicker as well

The battery warning light does not ever come on when this happens but the battery warning light does come on when you first turn the key on so that is acting normally.

What do you think.....voltage regulator going bad, alternator going bad, or something else? I'll check the battery voltage and the alternator for charging voltage in a little bit, but outside of that what do you suggest.

Thanks in advance,

Glenn
One of the two carbon brushes on the voltage regulator is Burnt / worn to short.

As the damaged brush makes / looses contact you get a cyclic flux / pulsation..

Remove the voltage regulator and inspect the brush length, both should match, replace the unit as required.

.
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  #4  
Old 09-15-2013, 02:32 PM
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Kind of what I figured. Just for the hell of it I went and did some checks a few minutes ago. Battery voltage with car off. 12.77 volts. Battery voltage with engine at idle 12.36 volts (I have a glow plug relay with the 3 min afterglow timer in it) Battery voltage with engine at idle and high beams on (after the 3 min afterglow turns off) 14.20 volts. Battery voltage at 2000 RPM with high beams on 14-23-14.29 volts with a couple small dips to 14.09 volts.

Couldn't tell if the lights were flickering as it was daylight. I have to be out late tonight so I can take my meter with me and check it when the lights flicker just for the hell of it.

Since I will be getting a new regulator on order, I see Peach parts has several..Genuine MB, Bosch, Meyle, Hella, Any recommendations (I notice the price difference is pretty significant between some of them.

Thanks again for the help
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2012 Mercedes ML350 Bluetec 59K (hers)
2002 VW Jetta TDI 210K (mine)
1998 Volvo S70 T5 Turbo 161K (kids)
1994 Ford F150 4WD 243K (wood getter)
1983 Mercedes 300D 350K (diesel commuter)
1965 Corvair Corsa 98K (fun car)
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  #5  
Old 09-15-2013, 06:38 PM
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Stay away from Meyle, it is often reboxed Chinese junk. You just never know what you are going to get.

Best bet is Bosch for this part because the alternator is a Bosch unit.

I am quite certain the Genuine MB will be a Bosch in a M-B package.

Get whichever one of the two is cheaper.
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  #6  
Old 09-15-2013, 10:57 PM
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I agree with jay_bob

Quote:
Originally Posted by jay_bob View Post
Stay away from Meyle, it is often reboxed Chinese junk. You just never know what you are going to get.

Best bet is Bosch for this part because the alternator is a Bosch unit.

I am quite certain the Genuine MB will be a Bosch in a M-B package.

Get whichever one of the two is cheaper.
He means "Genuine MB" or a "Bosch"..

I have a drawer full of "failed" other brands, "in dire need" I take brushes from them to put on good used BOSCH units.

.
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Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1980 240D
1983 300D
1984 190D
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  #7  
Old 09-20-2013, 07:29 PM
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Just an update. Got the new regulator today and put it in. It was kind of a PITA to change as either the engine shock mount or the a/c hard line was in the way, but after about 30 minutes I got it done. Old regulator was a Meyle and whunter was correct, one of the brushes was worn down WAY more than the other one, maybe twice as much worn. Never seen brushes wear so unevenly as that but..... Anyway, started the car, battery light works as advertised when switch is on and turns off when car is running. Battery voltage checks are as follows: Engine off 12.77 volts. Engine idling 12.36 volts (3 minute afterglow still on). Engine idling with afterglow off 14.02 volts. Engine idling, no afterglow, high beams, radio, and heater blower on 14.00 volts. I won't know until tonight if the flickering has stopped, but I think it should be.

Glenn
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2012 Mercedes ML350 Bluetec 59K (hers)
2002 VW Jetta TDI 210K (mine)
1998 Volvo S70 T5 Turbo 161K (kids)
1994 Ford F150 4WD 243K (wood getter)
1983 Mercedes 300D 350K (diesel commuter)
1965 Corvair Corsa 98K (fun car)
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  #8  
Old 09-20-2013, 08:11 PM
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Uneven brush wear is normal, perhaps 10% difference not 2X.

It all has to do with the direction of current flow. With one brush are trying to transfer brush material to the slip ring and the other brush is trying to pull copper from the slip ring.
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  #9  
Old 09-20-2013, 08:34 PM
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I have a Hella brand regulator, they are made in Germany...Bosch Spain ones are ok too.
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  #10  
Old 09-21-2013, 12:33 PM
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The replacement I put in is a Hella.

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2012 Mercedes ML350 Bluetec 59K (hers)
2002 VW Jetta TDI 210K (mine)
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1983 Mercedes 300D 350K (diesel commuter)
1965 Corvair Corsa 98K (fun car)
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