Charging issue

Tiny
DIVIDES
  • MEMBER
  • 2015 HONDA ACCORD
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Car never shuts off while driving. But once a trip is completed it won't start without a jumper. After it starts charge is about 12.5v both at battery and at alternator positive cable. Strange, if it was the alternator, she would have shut off I assume while driving at some point. Driven it 40 miles this way with no issue until it is turned off, and again eight miles after that. No battery light on dash. Trickled charged the battery but she still did not start on its own. Corrosion at battery terminal. Cleaned it out but still. I leave it running while looking at the scanner and it is in the 12.34-12:54 range. Is there a fuse first of all before I remove the alternator to have it checked out?
Friday, December 10th, 2021 AT 7:28 AM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

The voltage you see is likely being provided by the alternator. However, it isn't enough. Voltage with it running should be approx. 14v. It is prolonging the battery from going dead when running, but it doesn't recharge it enough to restart the engine. The starter places a large electrical draw on it.

What is the voltage at the battery with the engine off? I have a feeling it isn't much different than what you mentioned.

Take a look at this link and let me know if this is what you have already done.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

I will watch for your reply.

Take care,

Joe
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Friday, December 10th, 2021 AT 7:56 PM
Tiny
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Voltage at battery with it off is good but when I do a load test it shows it to be weak. No matter what I do while car is running it is still at 11.20-12.60.
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Saturday, December 11th, 2021 AT 8:11 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
It sounds like the alternator is bad. At this point, I would recommend removing it and having the alternator bench tested. I have a feeling it needs to be replaced.

To get you started, here is a link that explains how (in general) to replace an alternator:

https://www.2carpros.com/articles/how-to-replace-an-alternator

If you look at the attachments below, they are the directions specific to your vehicle for replacing it. The directions start with disconnecting the battery, then the serpentine belt, and finally, the alternator.

Remove it and have it bench tested at a parts store. Normally, there is no charge for having it tested.

Let me know what you find and what I can do to help.

Take care,

Joe

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+1
Saturday, December 11th, 2021 AT 8:31 PM
Tiny
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Thanks.
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Saturday, December 11th, 2021 AT 8:42 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
You are very welcome. If possible, could you let me know if this takes care of the problem? I'm interested in knowing.

Joe
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Saturday, December 11th, 2021 AT 10:07 PM
Tiny
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Replaced alternator and all is good. Thanks for your help.
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Tuesday, December 14th, 2021 AT 7:58 PM
Tiny
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When I installed it and had the battery trickle charged. Installed everything and checked with multimeter battery for a second it was at 13.65 so I knew it was working. Turned it off till today. Started it up and it was at 12.65 using multimeter, strange. Then used the probe and checked the battery and it was showing 14.5, same at alternator, not sure what to believe anymore.
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Wednesday, December 15th, 2021 AT 8:23 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

That is normal. On today's vehicles, there is a constant (small) drain on the battery even when everything is off. The idea that it went to 12.65 doesn't surprise me.

Let me know if anything different happens, but if you see 14.5v with it running, that's perfect. You shouldn't have any more issues with the alternator for some time.

Please feel free to come back anytime in the future if you have questions. You're always welcome here.

Take care and I wish you and your family a Merry Christmas.

Joe
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Wednesday, December 15th, 2021 AT 5:47 PM

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