# 2003 E320: alternator or wiring problem?

**URL:** <https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689>\
**Category:** Maintenance/Repairs\
**Tags:** mercedes-benz, e-class\
**Created:** [April 14, 2013, 9:48pm UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689 "2013-04-14T21:48:00Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![lisachills](https://avatars.discourse-cdn.com/v4/letter/l/9de0a6/32.png) [@lisachills](https://community.cartalk.com/u/lisachills)\
**Post date:** [April 14, 2013, 9:48pm UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689/1 "2013-04-14T21:48:00Z")

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Hi, my 2003 E320 (131K miles) had been intermittingly flashing a red “Battery/Alternator Stop Vehicle” light and annoying alarm sound as well as a “Malfunction Electrical Consumers Turned Off” sign. Then three days ago the “check engine” light came on; went away the next day. Then yesterday the engine completely shut down on me. The car started the today; took it to mechanic who says it could be alternator or wiring problem. Suggested I take it to MB dealer to get diagnosis before shelling out 800 bucks on an unnecessary car part. My question: should i take it to MB dealer or just replace the part? (I am not original owner; don’t know if alternator’s ever been replaced). Thanks for the advice.

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**Author:** ![knfenimore](https://avatars.discourse-cdn.com/v4/letter/k/9fc348/32.png) [@knfenimore](https://community.cartalk.com/u/knfenimore)\
**Post date:** [April 14, 2013, 10:02pm UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689/2 "2013-04-14T22:02:42Z")

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Any mechanic or auto parts store can tell you if your charging system or battery is bad. A simple volt meter can tell you. !2.5 volts for the battery and 14.5 volts if the car is running.

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [April 15, 2013, 5:35am UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689/3 "2013-04-15T05:35:48Z")

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@lisachills take it to a Benz dealer. I used to be a Benz technician for many years, and I can tell you from personal experience that there are many possibilities for your warning message:

Weak/old battery  
Failing alternator/voltage regulator  
Failing battery control module  
Battery control module needs software update  
Parasitic draw, which causes the battery to be in a perpetually low state of charge

This is that battery control module. It may be the $800 part that your mechanic was talking about.

> **[Mercedes-Benz](http://www.rmeuropean.com/Make/Mercedes-Benz.aspx)**
>
> Thousands of new OEM and aftermarket Mercedes-Benz parts in stock. Easy to use on-line catalog. Two-year parts warranty and free shipping on $65+ orders.

Again, I HIGHLY recommend that you take it to the Benz dealer only, and nobody else. They have the latest technical service information and latest parts. They can easily perform any needed software updates.

If anybody tells you that you need an alternator, I also highly recommend going to the dealer, as there were some updates on the voltage regulator. Usually, the only part of the alternator that went bad was the regulator, which was fairly easy to replace. Unfortunately, like I said, it was superseded, so I’d want to get the very latest part from the Benz dealer, if that was in fact the problem. A lot of customers were pleasantly surprised to learn that a relatively cheap regulator fixed the car, versus an expensive alternator.

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**Author:** ![lisachills](https://avatars.discourse-cdn.com/v4/letter/l/9de0a6/32.png) [@lisachills](https://community.cartalk.com/u/lisachills)\
**Post date:** [April 16, 2013, 5:01am UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689/4 "2013-04-16T05:01:29Z")

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Thanks soooo much for the advice! The folks at [cartalk.com](http://cartalk.com) rock!!

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**Author:** ![db4690](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/db4690/32/2583_2.png) [@db4690](https://community.cartalk.com/u/db4690)\
**Post date:** [April 16, 2013, 5:58am UTC](https://community.cartalk.com/t/2003-e320-alternator-or-wiring-problem/78689/5 "2013-04-16T05:58:37Z")

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@lisachills You’re welcome.

Good luck.

Please post post back with the fix.

Many of us enjoy reading the resolution to such problems.