This is a 1991 300D 2.5 Turbodiesel. Monday morning I started it up in the garage and most of the "idiot lights" in the dash stayed on. Some glow brightly (Battery, ABS), some moderately bright (parking brake) and some dim (oil, coolant). Here is what it looks like with the engine running at idle:



The ABS light goes off temporarily when the engine revs above 1000rpm. I searched the archives last night and what I found indicated that the regulator/brushes might be bad. I bought a new regulator and removed the old one about an hour ago. The brushes were very short so I was sure I had found my problem:



BUT I was wrong! After installing the new regulator, there was no change in the dash lights. Some additional info:

I put a voltmeter on the battery. After driving two solid days like this, about 70 miles with half of that before dawn with the headlights on, the battery reads 12.80V at rest. That is fully charged. When I start the car and let it idle, the voltage actually drops down to about 12.60, but goes up to 12.65-12.70 when I rev up the engine. Turning on the headlights takes it down to about 12.45 but again the voltage increases slightly when I rev up the engine.

So, what could it be? The alternator must be doing something or the battery would not be maintaining such a high voltage, but it's definately not working to it's full potential. Should I bite the bullet and buy a rebuilt alternator? Could it be some other electrical gremlin?

Thanks in advance for any replies,

__________________
-Dave

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1M30LAGSC1NU1AGYA9&year=1991&make=MB&model=300-DT-003&category=P&part=Overload+Relay

What would cause some lights to be dim? My OVR is new.

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joel

Prayers bring forth enlightenment.

Arthur,

How can one be sure that the OVR is the problem? It seems most people with a bad OVR are not able to start their cars - mine starts fine.

I think I am going to remove my alternator and have it tested before I spend any more money on other parts.

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-Dave

Give the OVP [ OVR to you] a good wiggle and watch the light .. the problem with OVP when there are lamp and ABS gremlins is the connections in the base ... give it a try , as it is in line with power feed .. also, pull the fuse on top and clean it and re-install.
These are just diyer things to try when one has no electronic diagnostic tools/meters/schematics..

Already removed the fuse, verified that it was not blown, and reinstalled. It is not plugged into a base but is hanging loose near the two computer modules. I will take another look at it tomorrow when it warms up a little.

Thanks,

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-Dave