Alternator/Voltage Regulator Fault Diagnosis
Thread Starter
Newbie
Joined: May 2012
Posts: 12
Likes: 0
1999 C230K
Alternator/Voltage Regulator Fault Diagnosis
So replaced the voltage regulator on my W211. (2007 E350-PZEV; 194K Miles) about two weeks ago. Easy fix and old VR was definitely at fault with the contacts extending to the pony they were falling out of the plastic. I’ll add a pic if I can find the old part.
Yesterday, at the same time my brake light switch popped out of its seating causing “ESP inoperable visit workshop “ message and brake lights to stay illuminated, I got a red-battery warning.
After reseating the brake switch, ESP message went away, but battery warning remains.
From the dash- engine off- 11.4V. When running the voltage drops but stabilized around 11.2. Same as with bad VR.
Alternator, starter fuse block and battery connections verified intact and tight.
Is is there a bench test I can put on the VR(regulator)?
I’m hoping it’s merely a bad part I can replace under lifetime warranty from fcpeuro. Otherwise it’s a new $300 alternator
🤢
i remember reading somwhere these alternator’s output is computer controlled. Is it possible a faulty module or relay is causing no-charge condition?
Next: pulling alternator off car for any
Yesterday, at the same time my brake light switch popped out of its seating causing “ESP inoperable visit workshop “ message and brake lights to stay illuminated, I got a red-battery warning.
After reseating the brake switch, ESP message went away, but battery warning remains.
From the dash- engine off- 11.4V. When running the voltage drops but stabilized around 11.2. Same as with bad VR.
Alternator, starter fuse block and battery connections verified intact and tight.
Is is there a bench test I can put on the VR(regulator)?
I’m hoping it’s merely a bad part I can replace under lifetime warranty from fcpeuro. Otherwise it’s a new $300 alternator
🤢
i remember reading somwhere these alternator’s output is computer controlled. Is it possible a faulty module or relay is causing no-charge condition?
Next: pulling alternator off car for any
Last edited by c_c230k; Oct 25, 2019 at 12:45 PM. Reason: Added mileage
Senior Member
Joined: May 2013
Posts: 336
Likes: 27
05 W211 E500, 03 C215 CL55 AMG
Sounds like a bad diode in the alternator.
Highly doubt a new bosch VR is failing.
There is a relay that switches charging on/off for SBC equipped cars but yours does not have that.
Corroded Driver SAM can cause no charge but unlikely as well.
Highly doubt a new bosch VR is failing.
There is a relay that switches charging on/off for SBC equipped cars but yours does not have that.
Corroded Driver SAM can cause no charge but unlikely as well.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,549
From: MA
2008 E350 4Matic, 2011 E350 4matic
I would get the alternator from Autozone, it's a rebuilt Bosch and also has the same lifetime warranty that FCPeuro has, but you don't have to mail it to them, just go to your local store. With the 20% discount codes found on retailmenot and even on their website, it's under $200 for the rebuilt one. I don't think it makes sense to replace the regular on a post face lift car as it takes as much trouble to replace the alternator. It was easier on the older models. The older models also had a battery control module, but I don't believe yours does. Also if your battery is weak, don't let the alternator charge it up, put it on a charger. If you don't have one, most auto parts stores will charge it up for free.
MBWorld Fanatic!
Joined: Jan 2009
Posts: 9,224
Likes: 1,798
From: V E G A S
1922 Ford Model T / no OBD
So new VR did not fix the charging warning?
Brushes are the only wearable on alternators, but old rings might need cleaning and diodes can burn occasionally,.
I remember most of automotive places will do free alternator test for you.
I had bad experience with such testing, but that's a start.
I still would remove new VR and inspect the rings.
New VR are made in India?
Brushes are the only wearable on alternators, but old rings might need cleaning and diodes can burn occasionally,.
I remember most of automotive places will do free alternator test for you.
I had bad experience with such testing, but that's a start.
I still would remove new VR and inspect the rings.
New VR are made in India?
MBWorld Fanatic!
Joined: Apr 2007
Posts: 2,381
Likes: 29
E
I would get the alternator from Autozone, it's a rebuilt Bosch and also has the same lifetime warranty that FCPeuro has, but you don't have to mail it to them, just go to your local store. With the 20% discount codes found on retailmenot and even on their website, it's under $200 for the rebuilt one. I don't think it makes sense to replace the regular on a post face lift car as it takes as much trouble to replace the alternator. It was easier on the older models. The older models also had a battery control module, but I don't believe yours does. Also if your battery is weak, don't let the alternator charge it up, put it on a charger. If you don't have one, most auto parts stores will charge it up for free.
FCP’s Bosch reman is $100+ more than autozone hence some skepticism
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,549
From: MA
2008 E350 4Matic, 2011 E350 4matic
Looked pretty much the same as the one I took out only newer and cleaner. Got it last year and it's still working fine. It was listed for $215 when I got mine, price went up $13 in a year. After coupon code mine was $185.
Trending Topics
MBWorld Fanatic!
Joined: Apr 2007
Posts: 2,381
Likes: 29
E
although my alternator still puts out 13.5v+ the whining concerns me as it sounds like a supercharger so time to go I think.
Sorry to thread jack but figured my Q also ties so OP may go down same route.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
Likes: 1,549
From: MA
2008 E350 4Matic, 2011 E350 4matic
Also had it shipped to me. They had crazy shipping, ordered it at around 6pm in the evening and they ended up shipping it at 9pm and I had it the next day. Mine might have been making noise briefly too, it was just burned up one day and I had the battery low warning come on so I knew it was probably bearings that were probably also shot in addition to voltage regulator.
Thread Starter
Newbie
Joined: May 2012
Posts: 12
Likes: 0
1999 C230K
Will pull alternator this weekend to replace.
After VR replacement the vehicle ran great and charged at 14.1 for 2 weeks/350 miles.
Is there a bench test for VR or do MB mechanics just swap and see if it works...doesn’t sound like a good German procedure.
Thanks!
