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Alternator replaced - dash battery light still ON

Tiny
ULTRARUNNER164
  • MEMBER
  • 2002 HONDA CRV
  • 2.4L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 194 MILES
I was on the road and dash gauges went crazy - went to shop and they said battery wasn't charging and suspected alternator. Replaced alternator and battery charging but dash battery light won't turn off. We had spent 2 nights in hotel waiting for vehicle and the mechanic sent us on our way with battery light still on, because he wanted to help us save time, and he couldn't find out how to get the battery light to turn off. He said the battery is charging and alternator replaced. All seems well with car, 2 days and 700 miles later, but the battery light is still on. Can you help me with what the problem is?
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Friday, July 6th, 2018 AT 12:09 PM

6 Replies

Tiny
WALLY AB
  • MEMBER
  • 97 POSTS
Has he actually done a load test on the battery? I would make sure again battery and alternator are fine. If it is, you likely have a parasitic draw somewhere draining the battery. If the battery connections are dirty too clean them up to make sure you have a solid connection to begin with.
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Friday, July 6th, 2018 AT 12:40 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,452 POSTS
I would start by having a different shop load test the system to be sure it is charging. The light gets a signal from the alternator to the ECM, which sends the signal to the dash through the com lines. I attached the wiring diagram and how to test the indicator, but you need a scan tool to be able to see if the signal is actually getting through or if there is an error in the system. It is possible the alternator failed in a way that damaged the circuits in the ECM and caused this issue. That would mean replacing the ECM to get the light to turn off.
It is also possible that there is a bad connection at the alternator that is causing this.
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Sunday, July 8th, 2018 AT 5:37 PM
Tiny
ULTRARUNNER164
  • MEMBER
  • 6 POSTS
A shop checked it out. The new alternator that was installed 800 miles away was working partly and charging the battery okay. But, upon closer inspection there was actual a fault in the new alternator of some sort. So they swapped it out with a new one and the light is now off on the dash and everything is charging as it should. Thanks for your help!
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Thursday, July 12th, 2018 AT 1:09 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,452 POSTS
I hate to say that I am not surprised that you got a defective unit. Almost seems to be the normal issue these days, just keep swapping the "new" part until you find the one that actually works.
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Thursday, July 12th, 2018 AT 1:55 PM
Tiny
ULTRARUNNER164
  • MEMBER
  • 6 POSTS
The mechanic at the little shop I took my car to, said that he will not put the "big box stores" auto parts in (like O'Reilly or NAPA for instance). He has a guy who rebuilds them whom he trusts and so we went with one of his. Thanks again
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Thursday, July 12th, 2018 AT 1:59 PM
Tiny
STEVE W.
  • MECHANIC
  • 13,452 POSTS
He is a lucky shop. The places that rebuilt them around me have almost all shut down.
Thank you for using 2CarPros. Stop back anytime with your automotive questions.
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Thursday, July 12th, 2018 AT 7:46 PM

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