Battery alternator

Tiny
DIONIS1
  • MEMBER
  • 2005 MERCEDES BENZ C220
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 196,000 MILES
Not always but quite frankly when I'm driving and I press more than 60-70% throttle my car gives me the battery alternator check along with 3-4 more checks. Of course, my lights dim, my A/C stops, my radio stops etc. This might go on for long or even as little as less than a minute and the car will go back to normal. Normally when I don’t rev more than 3,000 RPMs it doesn’t happen. It’s annoying and I don’t know what causes it since it has been to the workshops and it didn’t show. I can't always get it that's why yesterday it didn't happen. Today it kept happening. Can you help! Also, my voltage is as it should be?
Sunday, May 15th, 2022 AT 7:18 PM

1 Reply

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
The most likely cause of something like this is a faulty alternator that is not able to keep up with the load when the RPMs go up. Basically, when the engine revs up there is more of a demand on the electrical system and so the alternator will put out more voltage.

Here is a video on how to test the alternator. Basically, you need to perform the load test that is towards the end of the video.

https://youtu.be/Z-p4dMJUpUw

Turn as much of the electrical system as you can and then rev the engine and see what the voltage is. Basically, it may be able to keep up when it is idling because the demand is lower and so it can keep the battery alive due to the issue only happening a small amount of the time.

This will tell us if the alternator is keeping up with the demand or not.

Let's start with this test and we can go from there.

Thanks
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Monday, May 16th, 2022 AT 3:40 PM

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