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  #1  
Old 10-23-2002, 04:17 AM
cgeorge430
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Gilly, Any idea on an occasional "headlights go dim" all of a sudden thing?...

I have a 99 ML430 and I sometimes experience the headlight going dimm for about 1 sec, including the dash lights. It's like something is drawing lots of power all of a sudden and it causes the lights to flicker. It doesn't happen all the time...about 2-3 times having own the car for about 1 year.

This only happens when I'm at idle, brakes applied, in Drive gear and stopped in traffic.

It's not the aux fan cycling or a/c coming on. Doesn't seem to be anything electrical that I notice.

Anyone have any ideas? Someone suggested it might be an internal engine pump of some sort.

Thanks

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  #2  
Old 10-23-2002, 09:19 AM
Gilly's Avatar
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Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
Never really noticed this on another one.
I've heard some people complain of alternator failure, possibly this is the cause, an intermittent alternator failure. I could see why it may only be noticed in that particular circumstance, just at idle. It probably would be unnoticeable going down the highway unless it happened for more than a few seconds, and even then probably only at night. If it happened more often, your mechanic could monitor the alternator output and verify the problem. If it rarely happens, it'll be tough to verify unless it becomes more frequent.
Nothing else comes to mind regarding a sudden high load like this. The pump they're referring to doesn't ring a bell. Maybe the electric air pump for emissions? This only runs for a couple minutes upon a cold start, and also just for a second, sometime after a cold start (can't remember the timing spec on this) while the engine control module runs a check of the systems. After that it won't run again all day unless the vehicle sits for a long period of time and cools down enough. I've never noticed this causing a large current draw though.

Gilly
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  #3  
Old 10-24-2002, 02:23 AM
cgeorge430
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thanks very much Gilly, will bring it in to MB to check.

.
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  #4  
Old 11-21-2002, 12:43 AM
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Join Date: Jan 2000
Location: Fl
Posts: 140
Lightbulb similar...

Regarding this sudden drop in power. On my ML (98 320) I noticed that there is some sort of component engaging every so often. Very similar to the AC compresor cycling, the only thing is that this also happens with AC off and it also causes a small drop in RPMS which in turn also cause a slight decrease in light output (noticeable in the interior lighting and headlamps). I thought it might be the airpump, but now Gylly says it is not. The SA said it was the AC compresor that come cycles on and off all the time, even when AC is off (somehow I don't believe this), and that all MLs run a bit rough (shaky).
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  #5  
Old 01-23-2003, 05:30 AM
dOUG11
 
Join Date: Jun 1999
Location: Melbourne , Australia
Posts: 33
Hi,

I have the same issue with my 200 ML320. I thas been like doing that since new - I assume it is nothing.

Doug
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  #6  
Old 01-24-2003, 01:18 PM
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Join Date: Apr 2002
Posts: 139
the g has done that twice in the first 10k. stopped at a light, nothing on, but the headlights. ( edit nice, definitive clicking sound before it happens? )

i only get to drive it when it needs fuel , so it might do it more frequently.

i am hoping the eletrical gremlins will get hungry and eat something. i am thinking the electric cooling fan freaks out like cosmo kramer.
starts and then turns off.

i had the 210 wagon programed to run the electric fan all summer and then deprogrammed off durring the winter. i'm not sure of what the relays sound like when they kick in.
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  #7  
Old 01-24-2003, 06:42 PM
Hang up and drive MORON!
 
Join Date: Apr 2001
Location: Indianapolis
Posts: 96
Our 98 ML suffers from Cosmo Kramer 'sudden dim-age' woes.

<<< wishing it had a voltmeter
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  #8  
Old 10-16-2003, 01:54 AM
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Join Date: Jan 2000
Location: Fl
Posts: 140
its the electric fans...

I have payed much attention to this. As I see it, the current draw form the aux fans causes this I believe. I am inclined to think this as some folks have had their fans and wiring changed after repeated fuse #44 failures because of too much current draw. And I have seen the drop in lamp output just as the fans kick in.

my $0.02

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'02 C240
'00 LR Discovery
'72 280SE
'67 280SL

---past---

'79 280E sold (RIP)
'86 300E sold
'87 300SDL sold
'90 Laforza sold
'95 320SE sold
'98 ML 320 (sold)
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