Right side went dim:

With just the parking lights on they light up normally. With the headlights on, both the right parking light and headlight are very very dim.

ALSO !!! Car is stalling when I turn the brights on.

I put in a new H7 and nothing changed. Somebody tell me what in the world is going on.

Find the ground points on the right side under hood ( passenger ) and clean them as well as any other ground points under the hood. Pay attention to the wire where it is crimped to the terminal.

I just did a 06 Chrysler that had ground wires corroded off. Ended up fixing 3 ground points totaling about 30 wires.

Thank you Sir, would you happen to have a picture of where it is located?

My saga just got worse in the last hour. See my new post.

My 97 E320 is a parts car so I don't recall exactly where the ground points are. They are visible under the hood. Look for a stud and lots of wires going to it.

benz99999, I suspect the voltage regulator brushes are so worn that the alternator is not recharging the battery sufficiently. I am in the process of replacing the voltage regulator in our 1998 E320. You need to remove the alternator, then remove the cover on the back of the alternator to access the voltage regulator. Be sure to disconnect both battery cables before you begin this job.

After you disconnect both electrical leads on the back of the alternator and remove both E14 torx head bolts, use a pry bar to swing the alternator clear of the mounting bracket. To facilitate reassembly move the 2 sleeves in the mounting bracket slightly forward so there is adequate clearance to easily reinstall the alternator in the mounting bracket.

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Fred Hoelzle

Ferdman got it, exactly. These cars wont run with low voltage BC the fuel pressure drops and injection doesnt work..or some similar voltage related issue. They will not start with low battery even though well able to crank. Then charged up, the operation is fine. Your headlights or maybe the fan on high would do the same thing. Many issues have been corrected by a replacement alternator or battery.

Except he is having dim lighting only on the right side. Clean the grounds / check to see if the wire corroded where it is crimped into the eyelet.

Good point 97 SL320, more specific troubleshooting needed..Maybe using a continuity test/ohm meter on that headlight circuit for both shorting and for the ground resistance. A badly grounded or weakly fed headlight isnt going to drop the voltage to the systems and cause cut out..just a dim headlight, right? But one which is shorted from the positive feed just might do it..Esp if the alternator is failing..It could actually be at the fuse..which corrode on these cars. And left and right have different fuses if I recall. Others are far more accurate in the systems details than I am..

Hope to hear the conclusion..

Mercedes ( and some other cars ) put a bunch of ground eyelets on one stud. When the bottom one ( closest to the chassis ) corrodes it takes the others with it. Problem here is the upper grounds will seek ground through each other leading to a while raft of odd behaviors.

When the high beams are on more power is consumed and a different ground wire is used ( if there are two bulbs in the system ). Think of how a dirty battery terminal works at low power but fails at high.