Voltage regulator, alternator or battery?
Thread Starter
Member
Joined: Sep 2013
Posts: 78
Likes: 2
C240 4MATIC
Voltage regulator, alternator or battery?
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.
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.
Junior Member
Joined: Jan 2013
Posts: 57
Likes: 1
2003 C230K & 2007 C230
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.
MBWorld Fanatic!
Joined: Sep 2011
Posts: 1,657
Likes: 35
From: Austin, TX
2005 C230K(sold), Mk7 Jetta
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?
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?
Member
Joined: Mar 2013
Posts: 174
Likes: 2
From: Mississauga, Canada
2003 CL203 C320, 2002 W208 CLK320 cabriolet, 2012 A207 E350 cabriolet, 2011 X204 GLK350 4matic
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.
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.
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Joined: Mar 2008
Posts: 3,714
Likes: 56
From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
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.
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.
Member
Joined: May 2007
Posts: 125
Likes: 1
From: TORONTO
C230 KOMPRESSOR (2003)
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.
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.
MBWorld Fanatic!
Joined: Sep 2011
Posts: 1,657
Likes: 35
From: Austin, TX
2005 C230K(sold), Mk7 Jetta
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
(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
Last edited by VVF; Apr 25, 2014 at 12:00 AM.
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Member
Joined: Nov 2007
Posts: 171
Likes: 1
From: ontario, Canada
C230 COUPE 2003 M271
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.
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.
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Junior Member
Joined: Aug 2008
Posts: 58
Likes: 1
From: Ont, Canada
2005 C230K coupe
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.
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.
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,105
Likes: 11
From: Toronto, Canada
2019 C300 Wagon; '75 Triumph TR6; previous: 2004 C230 6spd sold after 17 years of driving
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/
Cheapest place to get is http://www.americanenginesco.com/alt...ge-regulators/
Thread Starter
Member
Joined: Sep 2013
Posts: 78
Likes: 2
C240 4MATIC
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.
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.
How did you trace it to the wire though?
Thread Starter
Member
Joined: Sep 2013
Posts: 78
Likes: 2
C240 4MATIC
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.
