Hey Darinkald,

I just went through a bunch of alternator testing and repair on my 1989 300E. Similar symptoms. My car comes with a stock Bosch 70A alternator. I had dimming lights, slow wiper and weak wiper motor.

I would first verify that you have a good battery. Get it tested to make sure it is holding a good charge. Also check your serpentine belt (or poly belt, whatever your engine has) for tension and wear. Since you've checked your electrical connections already, I would suspect the alternator.

I found out that the stock 70A alternator is kind of underpowered for my car and Mercedes upgraded to an 80A alternator in 1990. The 70A just doesn't crank out enough current at low RPMs. So I replaced my ailing stock 70A with a new Bosch 80A alternator. Car runs perfectly now. You may have a similar problem with your car. Did you buy a Bosch alternator or a different brand?

Your voltage readings seem kind of low. The battery should have a resting voltage closer to 12.5-12.8 if it is in good shape. The charging voltage should stay above this even with a strong load being applied (mine doesn't dip below 13.5V even with a full load).

Good luck!

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon