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Discussion Starter · #1 ·
I bought my 2012 Civic about 5 years ago, and in that time I've replaced the alternator 4 times and the battery 3. I've had various auto parts stores test the battery/alternator, and I've been replacing them at their recommendation. Until recently, I've always purchased remanufactured/lifetime warranty alternators from the big box stores, and within a year my car won't start and the alternator fails their test.

After being stranded an hour away from home and having another parts store tell me the alternator failed, I figured I'd take it to Honda to see if they could diagnose any other underlying issues (tensioner or something like that), but they said it was just the alternator. I bought a new OEM alternator from them and installed it myself over the weekend.

I went to a parts store to have them test it for my own sanity, and they said the voltage regulator has failed. I haven't had any issues starting yet, but I decided to check the voltages myself:

Battery with car off (after drive for about 20 minutes): 12.75V

Voltage at battery leads with engine running (all electrics off): ~12.75-13V

Voltage at battery leads with engine running (radio, seat heaters, headlights, etc. on): 12.25V


Those voltages with the car running don't seem high enough, and it seems crazy that a new OEM alternator would be like that nearly out of the box.
 

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denso new / reman or nothing...

you running some crazy sub and amp setup in that thing?

the voltages do seem low... its possible you have ground or cable issues between the alternator and the battery.
 

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Discussion Starter · #3 ·
denso new / reman or nothing...

you running some crazy sub and amp setup in that thing?

the voltages do seem low... its possible you have ground or cable issues between the alternator and the battery.
Do you know if Denso manufacturer's the OEM? I have LED headlights and an aftermarket stereo, but no additional amps or speakers. The stereo was added within the last few months, but I've been having electric problems for years. I'm not saying it's not related, but it seems unlikely.
 

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Discussion Starter · #4 ·
Just to throw this out there too, the battery terminals/connectors are super clean.

Would testing the alternator voltage from the connector plugged into the alternator be a good way to rule out wiring issues?
 

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2012 CBP FG4
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I bought my 2012 Civic about 5 years ago, and in that time I've replaced the alternator 4 times and the battery 3. I've had various auto parts stores test the battery/alternator, and I've been replacing them at their recommendation. Until recently, I've always purchased remanufactured/lifetime warranty alternators from the big box stores, and within a year my car won't start and the alternator fails their test.

After being stranded an hour away from home and having another parts store tell me the alternator failed, I figured I'd take it to Honda to see if they could diagnose any other underlying issues (tensioner or something like that), but they said it was just the alternator. I bought a new OEM alternator from them and installed it myself over the weekend.

I went to a parts store to have them test it for my own sanity, and they said the voltage regulator has failed. I haven't had any issues starting yet, but I decided to check the voltages myself:

Battery with car off (after drive for about 20 minutes): 12.75V

Voltage at battery leads with engine running (all electrics off): ~12.75-13V

Voltage at battery leads with engine running (radio, seat heaters, headlights, etc. on): 12.25V


Those voltages with the car running don't seem high enough, and it seems crazy that a new OEM alternator would be like that nearly out of the box.
Seat heaters?? Dang, that'd be nice. What trim is this?
 

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Discussion Starter · #7 ·
Found an interesting piece of information on another thread:

you get what you pay for a battery definitely rule #1. when I worked @ advance auto we pushed the autocraft gold's because they really are the best product that johnson controls makes as far as the plate grid setup is very strong. I do hook up a float tender to our vehicles on occasion the temp overnight drops below the 30's so the battery is nice and "warm" with plenty of charge ready to go. if you watch with a volt meter on these newer gen honda's you'll see they do "charge" the battery very unusual and will generally report a failed alternator on many store test equipment.
That makes me wonder if I even have a problem, or the generic testers at the auto parts stores are throwing up a false reading.
 

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With the frequent use of the high load options in the vehicle battery and alternator replacement will be more frequent.
Use a high quality battery or replace with an AGM battery of the same battery type for longer life. Temperatures too cold and or too hot, ambient or under hood temps, will shorten the life of a lead acid battery much faster.
These vehicles come with an Electronic Load Detector, which has a resistor located under the junction box near the driver’s fender under the hood. The ELD sends voltage readings to the ECU through a single wire connector on the alternator. When the vehicle has. I loads at idle it is not uncommon for the ELD to hold a “good” battery at 12.2 volts and can even dip below 12 for short periods of time. As you command more voltage from the battery, the ELD sends the signal to the ECU and the ECU commands the alternator to increase charge volts. This is a constant change and will seem sporadic if monitoring the voltage as you drive, volts dipping as you decelerate for example.
Alternator life is going to depend on the alternator you buy and whether it’s remanufactured or brand new.
With all that said, any aftermarket electronics that you have connected to the battery terminals is bypassing the ELDs capability of reading if the extra draw, therefore will not command the alternator to increase voltage.
 

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2012 Honda Civic LX
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Honda's ELD is in my opinion what keeps all the electronics working a happy long life. My 2012 Civic LX has seen the battery replaced 3 or 4 times now, I can't remember. The alternator IS original and keeps on doing its job. It is possible that your ELD is failing intermittently though I don't know if Honda maybe has a way of diagnosing this further. I do know that a failed alternator will cause the battery light on the dashboard to illuminate all the time. There are some occasions where the battery light will come on my Pilot's dash and simply turning off the engine, letting it sit for a moment, then starting it up again and all is good, no more light. I believe this might be caused by a ground wire somewhere getting ready to bite the dust because they will attract the corrosion the most as they age and probably more so in moist environments. I will also attribute the lack of issues on both my Honda vehicles to the fact that they were/are garage kept and not left outside (civic is no longer garage kept since we bought the pilot 2 years ago)
 
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