blzdout

My car is almost perfect. When I got it, it was literally a piece of ****. I've been fixing her myself for the past year & she's almost 100%. I know have an Idle/voltage issue. Not the typical dirty MAF/Throttle plate idle. My electronics flickers & the car shakes really badly @ idle.

I used the handy voltage meter in my cluster (excellent feature) while driving & noticed that my voltage was very unstable. When I first start the car, it goes to the normal 14.2v. Driving around, still a stable 14.2v. When it comes to a stop, it goes from 14.2 to 14.1. Driving around again, it's still going from 14.2 to 14.1. Idle, 14.1 to 13.9 back & forth. Well, you get the picture. It'll keep dropping & dropping. The lowest I seen it go was 13.0v, which made my car shake really badly.

I have 3 Ideal solutions:

-Fully charging my battery & getting it tested. If battery is good & still flickering/idle problem

-Replacing my voltage regulator. If that doesn't work...

-Replace the alternator.

Car has 177k miles & still no major problems. Besides the fact I used to stall in the middle of traffic, fixed that by installing a new fuel pump (right unit) myself.

Does anybody have any experience with this? I would flat out replace the alternator but idk, wouldn't the car just completely die out if the alternator was completely bad? The problem reminds me of a dying battery in a remote. Take a battery out, flip it around & it'll work as if it was fully charged for a short period of time.

Lgraz5

You may want to investigate further. FWIW, my alternator and battery needed replacement but the only symptom was an occasional (happened three times) "Check Battery/Alternator" message over a six month period. Car ran so well (and voltage was so good) I thought the message was an error until the day the engine turned itself off while on the highway.

VVF

If the car was a piece of it, I bet the alt hasn't ever been changed.
At this point I'd just replace the whole thing e.g. with a reman unit for ~$200, for the peace of mind.
On a C240 it's just two bolts if I remember correctly?

Alswag

VVF, I believe you're right. I think it's only two bolts and the belt.

blzdout, my car did the exact same thing you're talking about when I first got the car. It went away on it's own and never came back, however.

I would get your battery tested and if it's good, I would replace your alternator. As VVF said, it probably hasn't been changed since the car was new. You could get a refurbished one for pretty cheap, provided it fits.

Carsy

How old is the battery & is it the correct size?

Sounds more like a voltage regulator not keeping the correct settings.

I would load test the battery, check VR then Alternator in that order.

A free check up at an auto electrician may save you money.

Good luck.

ammar_rage

My two cents; i dont think your VR is acting up. Its quite normal to see that bit of a range during different engine speeds. And 13 V is not low enough to stall your equipment; if it were and when it is --> you get the Check Batt/Alternator message on the screen.

As for battery being old - it should not do what you are describing; more experienced members can weigh in on this; when the car is running your alternator picks up the load not the battery - But it is good idea to get the battery tested.

Now the alternator; for me the alternator works if my volt meter shows that the output is between 12.5 - 15 V. Its doing what is supposed to.

If I had to pick between the 3; i would start with the battery and not jump to Alt.

VVF

The voltage at idle should be ~13.6v, when you rev it to 2k should be around 14.4v with a healthy alt.
(That's for m271 though, but the numbers should not be that much different for V6's)

This thread might be an interesting read, too: https://mbworld.org/forums/c-class-w...regulator.html

wvadam

The car should give you the batt/alternator warning in red if there is something wrong with the charging system. I think you need to also consider that anything that causes your car's idle to drop very low to the point of shaking will make the voltage drop to the 12-13 range because its not turning the alternator fast enough. I had a vacuum leak that occasionally caused the idle to drop and sometimes stall at idle, but no symptoms on the highway and it didn't throw an engine code.

KillerPancake

Have you got a Valeo or Bosch alternator? What's the mileage on your car?

For a frame of reference.... I have the Valeo alternator. At 185K km (around 115K miles) I had the alternator off while performing some other work and decided to pre-emptively change the regulator/brush assembly. I wasn't having any alternator related issues at the time, but the brushes were really worn down and I think I caught it at the right time. It would not have been too much longer before that alternator was going to start acting up due to worn brushes.

VVF

Are you reading the actual posts or just the topic names? lol
His car is at 177k miles.

Boom vang

I have a Valeo alternator and there was a defect in the VR 2003-2004 that would throw an error. I replaced my VR with a new VR and been fine ever since

Cheapest place to get is http://www.americanenginesco.com/alt...ge-regulators/

blzdout

Thanks all. I plan on officially tackling the problem in the next upcoming weeks. I will post what fixes the problem.

blzdout

I fixed the problem by simply replacing a defective spark plug wire to cure a random misfire on cylinder 6 that popped up once in a blue moon. I had no clue it was that bad to cause my electronics to flicker & voltage to become very unsteady.

I ordered a used coil pack attached with 2 spark plug wires from a '99 e320 for $14.99 on eBay. The harness doesn't go all the way down but it goes down far enough to get the job done though lol.

VVF

How did you trace it to the wire though?

blzdout

I did the old switcharoo. Cylinder 6 was misfiring so I swapped the coil packs & wires around. Cylinder 5 misfired so I knew it was either the coil pack or wires from cylinder 6 that was causing the misfires. Then I swapped the wires around instead of the coil pack (moving the old wires from cylinder 6 back to cylinder 6) then cylinder 6 started to misfire again. I suspected 1 wire because it had a little corrosion in it. I put that wire back to cylinder 5, but I was wrong. Cylinder 6 still misfired so it was due to the other wire.