1995 E300D Alternator Problem? - PeachParts Mercedes-Benz Forum

GreenDiesel · #1 10-24-2011, 06:01 PM

For the last few weeks I had been noticing some noise at the front of my engine bay, like something was loose in the belt path, and had not been able to track it down (the sound would go away when I accelerated). My stereo was also cutting out at high volume.

Turned on my car this morning to let it warm up. Started up with no problems and none of the loose noise I had been noticing. Walked inside for a few minutes and when I came back out the car was still running noise free but all of my dash warning lights were on. I popped the hood checked everything out, all my fluid levels were perfect. Turned it off, turned it back on, no problem, lights still on. My initial research has suggested the alternator. Wiring harness is in good shape and was replaced last year so I doubt it's that. According to my records the alternator was replaced 4 years ago. I've heard the VRM can be pulled and the brushes replaced relatively inexpensively but I can't seem to find these parts for the 1995 E300D alternator. Anyone else experienced a similar issue? Should I go ahead and pick up a reman alternator on the way home? Price is pretty reasonable at around $150 and I know I can change it out myself with no problem.

layback40 · #2 10-24-2011, 07:03 PM

Noise needs to be investigated first.
The brushes do not make it.
Maybe bad alt front bearing.
When was the belt last changed?
Tensioner problems?
water pump bearing?

engatwork · #3 10-24-2011, 07:39 PM

Anyway to test the voltage at the battery during idle?

GreenDiesel · #4 10-24-2011, 08:37 PM

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Maybe bad alt front bearing.

I'm thinking that this is likely but the belt is still turning and I didn't see any resistance. Perhaps it didn't seize but still failed?

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When was the belt last changed?

Brand new belt as one two months ago

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Tensioner problems?

Tensioner pulley, tensioner shock and tensioner swing arm also replaced two months ago

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Water pump bearing?

Any way to test this?

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Anyway to test the voltage at the battery during idle?

Not tonight but I'm going to do a little more diagnosis in the morning

engatwork · #5 10-24-2011, 08:43 PM

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Any way to test this?

Remove the belt and spin everything by hand with the exception of the crank

. See if you feel any roughness or something that does not feel right.

GreenDiesel · #6 10-25-2011, 11:02 AM

I haven't released the tension on the belt to check the pulleys but I did throw a multimeter on the battery. It is reading between 11 and 12 volts at idle. Shouldn't it be closer to 13-14?

GreenDiesel · #7 10-25-2011, 11:36 AM

Well I blipped the throttle a couple times and the warning lights went off and stayed off. I'm still concerned that the alternator is going out or there is a loose connection I need to track down.

Zulfiqar · #8 10-25-2011, 11:38 AM

The alt is not charging - when the battery light comes on it also illuminates all other lights - its part of checking the working of the lights on every startup. The SRS and glow is not tied to it

I bet the regulator brushes are worn off. revving is not helping?

GreenDiesel · #9 10-25-2011, 11:52 AM

Revving got all of the lights to turn off. Any idea where I can get just the regulator brushes? I've checked Peachparts ********AZ ********* and a couple others but no luck.

Zulfiqar · #10 10-25-2011, 12:00 PM

if revving solved it then your belt is slipping because the alternator excites as soon as the engine reaches 500 rpm - its not an old vw diesel Golf which needs to be blipped to 1000 rpm to start charging

GreenDiesel · #11 10-25-2011, 01:27 PM

Decided to go ahead and drive to work. Twenty minutes in the dash lights came on and stayed on no matter what RPM the engine was turning at. I'm going to go ahead and order an alternator and see if that fixes my problems. The entire tensioner assembly is new as of three months ago and everything is tight, I can't see why it would be at fault here?

Zulfiqar · #12 10-25-2011, 01:35 PM

is there any alternator repair place nearby where you live, look it up in yellow pages, and ask them for a bosch internal regulator for your car, they would know. Some of these type of shops have better quality than the items you get from Autozone etc.

I had a camry alternator fail - full fielded it and found the regulator to be shot, got a new one and a new set of carbon brushes from such a shop and drove it for another 45,000 miles before I sold the car.

GreenDiesel · #13 11-01-2011, 02:10 PM

*UPDATE: Could not find just the regulator or the brushes. Had an alternator shop ship me their very last NOS Bosch alternator from their warehouse for $150. Pulled the old alternator out, very little resistance and lots of bearing noise when turning the pulley, it was definitely the source of the noise I had been hearing. Put the new alternator in, noise gone, dash lights gone and the radio hasn't cut out since.

Thanks for all the help!

Zulfiqar · #14 11-01-2011, 05:22 PM

Good that you solved your issue, a little off topic question but I see that your steering column has a beauty ring where the dashboard meets, I have the same car but it has no such thing and I cant see how one would fit, I saw a picture where it showed that the headlight trim piece has a slot for it, My car doesnt have it.. odd