Possible alternator problem?

Tiny
CJC719
  • MEMBER
  • 2001 HONDA CIVIC
  • 1.7L
  • 2WD
  • AUTOMATIC
  • 236,000 MILES
I woke up one morning and went to start my car and it just gave me the ol clicking noise. So I took the battery to O'reillys and they checked my battery and charged it. The battery read good and my car was running again but something still seemed off. So I took it to AutoZone and their test said the battery was bad. I finally decided to just go out and get a new battery and a multimeter. The new battery read goods when the engine is off and around 13.6 with it on. I noticed when I put the A/C on it drops to about 12.4. Also when driving for a while it seems to drop slightly too. Do you think it could be alternator instead? I'm just wondering why it tested good at AutoZone under load? My regular mechanic checked it out a couple months ago too, because my battery lights been on since I purchased it and he said alternator was good to? He said battery light was just needing to be reset.
Saturday, July 17th, 2021 AT 11:33 PM

24 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning,

You have a charging system issue with the alternator. The voltage should be 14 to 14.5 volts at the battery with the engine running.

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

https://www.2carpros.com/articles/how-to-check-wiring

13.6 is no good. It sounds like you have a bad diode in the alternator. You should replace the alternator.

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

As far as the battery, many people test batteries in different ways. It can test well today and fail tomorrow.

https://www.2carpros.com/articles/car-battery-load-test

Roy
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Sunday, July 18th, 2021 AT 3:48 AM
Tiny
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Thank you, I really appreciate it. I kind of figured it was the alternator but it's always good to have a professional opinion. Do you think it's something I should even attempt myself being it's probably my first DIY under the hood. I would like to be able to work on my own car eventually. But I just don't know if this would be a good place to start?
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Sunday, July 18th, 2021 AT 11:57 PM
Tiny
ASEMASTER6371
  • MECHANIC
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I think you can do it, just take your time. Follow the instructions and make sure you put back everything you take apart.

Roy
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Monday, July 19th, 2021 AT 3:15 AM
Tiny
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Okay, thank you Roy.
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Monday, July 19th, 2021 AT 6:51 PM
Tiny
ASEMASTER6371
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You are welcome.

Always glad to help.

Roy
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Monday, July 19th, 2021 AT 6:56 PM
Tiny
CJC719
  • MEMBER
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One last thing; is there any specific tools I need like a belt tensioner? I just have the basics, I know some videos are saying I need a jack stand but all I have is the basic jack the car comes with?
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Tuesday, July 20th, 2021 AT 11:12 PM
Tiny
ASEMASTER6371
  • MECHANIC
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No, basic tools are all you need for this repair.

A standard wrench will release the tensioner for the drive belt.

Roy
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Wednesday, July 21st, 2021 AT 1:13 AM
Tiny
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Is there a way to make sure the belt tension is correct? I know if it's loose it'll squeal or whatever.
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Monday, July 26th, 2021 AT 6:10 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
It needs to be taunt. Make it tight so there is no deflection in the belt.

Roy
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Wednesday, July 28th, 2021 AT 12:20 PM
Tiny
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  • MEMBER
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Okay, thanks again.
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Wednesday, July 28th, 2021 AT 12:45 PM
Tiny
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  • 14 POSTS
So I installed new alternator and the battery light was finally off when I started it, Everything seemed good. I was getting over 14 volts but when I turned the A/C on again it started to fall to about 13.2 and kept dropping like before. I figured maybe it was just because I was in idle. But when I drove it the next day the voltage dropped again but this time while driving. The battery light even shut on again for a few seconds. The belts are good too, nice and tight. I have no idea what's going on?
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Monday, August 2nd, 2021 AT 8:45 PM
Tiny
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I would have the new alternator tested. Remove it and take it back to the parts store and have them test it. It is a free service and they can check it off the car.

Roy
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Tuesday, August 3rd, 2021 AT 2:53 AM
Tiny
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Yeah, I did that and they said it was good. It reads fine until I put the A/C on.
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Tuesday, August 3rd, 2021 AT 2:27 PM
Tiny
ASEMASTER6371
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Okay, when you put the A/C on, what does the voltage drop to?

Roy
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Tuesday, August 3rd, 2021 AT 3:07 PM
Tiny
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It will keep dropping if I let it. The lowest I seen it go was around 12.4 and I shut the A/C off.
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Tuesday, August 3rd, 2021 AT 4:22 PM
Tiny
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Is the engine idle correctly? If the engine RPM drops, the charging rate will drop.

Roy
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Tuesday, August 3rd, 2021 AT 4:24 PM
Tiny
CJC719
  • MEMBER
  • 14 POSTS
Idle seems fine, it happened while driving yesterday. I felt like I was barely going to make it home. Do you think I over tightened the nut that connect the charging wire to alt? Or is it possible to over tighten alternator belt?
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Tuesday, August 3rd, 2021 AT 4:56 PM
Tiny
CJC719
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Disregard that last part because I'm sure it has nothing to do with over tightening or any of the work I done. Because this is the exact problem I had before installation. Also, I wanted let you know I drove around for a few yesterday without A/C and everything was good.
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Tuesday, August 3rd, 2021 AT 8:23 PM
Tiny
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I still think that the alternator is the issue. It may test okay on the test bench but under load, it may be failing internally since the A/C system does draw a lot of currents to make it work.

Roy
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Wednesday, August 4th, 2021 AT 2:28 AM
Tiny
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So you think the new alternator I bought from AutoZone is possibly bad? I know it happens, it's just crazy how it's the exact problem I had before and all the readings are fine with everything else on brights, radio, hazards, inside lights. It works fine when I put heater on or just the fan too, it's only when A/C kicks on.
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Wednesday, August 4th, 2021 AT 1:31 PM

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