[Sun_odyssey]

Hi my 2012 Honda Odyssey showed "check charging system" message and the red battery light. I found they appeared when the car stopped at the traffic light or speed is low. They disappeared when the car is continuously running at high speed, like 50-60 mile/h. I checked the voltage of the battery. It is 12.66 V when car is not running. It is 14.2 v when car is running at ~1000 rpm without electrical loads, such as AC, radios and headlights. It was 14.3 v when engine runs at 2000-2500 rpm without electrical load. At the full electrical load, the voltage drops to 12.8 v.

I found the alternator is somehow still charging the battery. Because I left the car in the garage for two weeks, when I came back to start the car, The battery was low and the car just barely started. But after I had the car run for 15 minutes, I shut off the car and restarted, I could start the car much faster.

So is the alternator bad? or something else is bad? Please help and share your opinions.

 

[WiiMaster]

Check the spool valve above the alternator for leaking oil.

 

[DanW]

I would get the battery load tested. Just because the battery has good voltage doesn't mean it has enough cranking amp to start the van. Also it would be nice to know how old the battery is and the mileage on the van.

 

[Sun_odyssey]

Check the spool valve above the alternator for leaking oil.

Check the spool valve above the alternator for leaking oil.

Oh, I forgot to mention that in May the van had a "check engine" light on, I had the Honda dealer checked and fixed. They found leak on valve cover gaskets and replaced it. Is it possible that the leak on Valve cover gasket damaged the alternator or their repair messed up the alternator? The van has only 81K miles. The battery is less than 2 years old.

 

[Sun_odyssey]

I would get the battery load tested. Just because the battery has good voltage doesn't mean it has enough cranking amp to start the van. Also it would be nice to know how old the battery is and the mileage on the van.

Thanks. I can start the van, just don't know what causes the "check charging system and red battery sign". The van has only 81K miles. The battery is less than 2 years old.

 

[DanW]

The oil from a leaking valve cover gasket could have dripped down on the alternator and damaged it but you said it was reading 14.2 volts while the car was running which is normal. Did the dealer replace the spool valve mentioned in the above post? The spool valve is just above the dip stick and has been known to leak oil down on the alternator and kill it. I would still check the battery and eliminate that possibility, even after sitting for two weeks the battery should turn over the engine easily.

 

[Sun_odyssey]

thanks for all your comments. Yesterday I went to auto zone to check the battery and alternator. They said the alternator is good. When they tested the battery, it shows "good", but only has 60%, and then they charged the battery. It took two hours to charge it to 82%, so they told me the battery needs to be watched. This morning, I went to auto zone again. the battery dropped to 50% overnight. So it seems that something drains the battery, or the battery does not hold the charge? Since my battery is still in warranty, I went to Walmart. They tested it, and the meter showed it is good, so they don't replace it. I will have a 8 hour-trip next week. Is this van reliable to drive? Or at least I need to replace a new battery? Thanks for all you comments!

 

[WiiMaster]

Do a parasitic draw test.

 

[oldskewel]

Thanks. I can start the van, just don't know what causes the "check charging system and red battery sign". The van has only 81K miles. The battery is less than 2 years old.

Those two things basically mean the same thing = that the car thinks the battery is not being charged by the alternator. And when I say "thinks," it is more complicated than in the olden days when it was a simple circuit with a wire and light bulb. Now the car's computer (PCM / ECU) makes that decision and controls the turning on of the light and the text message.

It could be that you have an intermittent fault in your alternator, and that it was working properly when Autozone tested it for you.

Your battery sounds good. Taking a couple of hours to charge about 20% is a good sign (charging much faster than that would indicate reduced capacity, which is what I find to be the most reliable test for when a battery is worn out).

If you have a parasitic draw, that can be tough to find for some people, especially if it is intermittent. The fact that your battery dropped to 50% is why @WiiMaster thinks you might have a parasitic draw. If you parked it, measured 82% (somehow), then 50% the next morning, that would indicate a serious parasitic draw. But if you were 82% at Autozone, with a malfunctioning alternator, drove it home (draining the battery), drove it to Autozone the next day (continuing to drain while driving since the alternator is not working), and they measured 50%, you could have a good battery, no parasitic drain, and just a malfunctioning alternator.

Having a voltmeter would be very helpful to you here. I would not go on a trip without one. You'll be able to measure voltage while the engine is running, to confirm whether or not the alternator works, and also the battery. More direct and useful than what Autozone or Walmart can offer you. I see your voltage readings in the original post - so hopefully that means you already have one. The store tests don't do much more than you can do with that, and add some confusion and inconvenience.

If I had to bet, I'd pick an intermittently failing alternator at this point, which would mean big problems on your trip.

I had a former problem on my 2011 with the charging light coming on. In my case it fixed itself eventually, after extensive careful debugging, but no repairs at all. This is a rare, but not unheard of issue on these cars. So I doubt that is your situation. In case any of that story helps, here is the thread:

Battery light on, alternator OK

UPDATE in AUG 2022 - following extensive debugging and no repairs at all, this problem eventually fixed itself and has been fine for over a year now. Still possibly useful info in here for others, but that was the "answer" in my situation. Still on the original alternator at 136k miles, having...

www.odyclub.com

 

[Sun_odyssey]

Yes, it is probably parasitic draw, because after the battery was charged to 82% yesterday, i took it back to my house and installed it in the van. Then this morning I drove the van to autozone for alternator test. Autozone was just a few minutes away (less than a mile) from my house. I doubt that short distance driving could get the battery drop from 82% to 50%. The van has a backup camera with two signal transmitters that i installed miserly 10 years ago. I believe the two transmitters are constantly using the battery even when the van is parked in garage. But they never caused any problem over the past ten years. I could not think of anything that could drain the battery overnight. I will do a parasitic draw test tonight.

 

[Sun_odyssey]

one more question: Even if there was a parasItic drain, can it trigger “check charing system” and “red battery”?

 

[DanW]

Why not charge the battery disconnect it from the van and let it sit overnight to see if it holds the charge. If it doesn't you know its the battery. If it does you know you have a parasitic draw.

 

[THE ELITE]

Hello i'm new here for the past year and a half i've been having the same issues with alternator. I had changed around 5/6 of them . I even tried the Denso brand but I still got the same message on dashboard? check charging system . Took it to an electrical shop / mechanic said that the ECM was good and changed the alternator. 3 months later same issue . This is frustrating . Any suggestions would be helpful .

 

[phattyduck]

Any oil leaks on the alternator? The battery sensor may also go bad or there could be other wiring issues.

-Charlie

 

[THE ELITE]

No oil leaks on alt.

 

[Sun_odyssey]

Why not charge the battery disconnect it from the van and let it sit overnight to see if it holds the charge. If it doesn't you know its the battery. If it does you know you have a parasitic draw.

I did the test as you recommended. I disconnect the battery at the night of August 10 till today. I measured the voltage on the yesterday's morning and this morning. Here is the result: the voltage starts with 12.51. On yesterday's morning it dropped to 12.48, and this morning it was 12.46. Obviously, it slowly drains itself overtime, but I am not sure it is a normal drain or a significant drain. Any experience on it? I will do a parasitic draw test by measuring the current today and post the result here. Thanks!

 

[Sun_odyssey]

Here is the update: my multimeter does not have 10 AMP for parasitic draw test, so I found on website a protocol to test alternator (below):
How to test the alternator
The easiest method to check the alternator is by measuring the voltage at the battery terminals when the engine is running.

1. Start your Odyssey.
2. Connect the black cable of the multimeter to negative terminal of the battery, and the red cable to the positive terminal.
3. The voltage should be between 13.5 and 14.8 volts with the engine running. (My battery is 14.3 v)
4. Switch on the accessories in your Odyssey, for example, headlights, AC fan at full speed, and interior lights.
5. The voltage should remain around 14 volts. If it drops and remain below 13.5 volts, it indicates a problem with the current supply from the alternator. (My battery started with 14.03 v and slowly dropped to 12.08 v and seems to be stable there. When I turned off all the accessories, it came back to 14 v.)
6. If the voltage drops below 12 volts with the engine running and the accessories turned on, it means the current supply from the alternator is completely cut off and all the electronics are solely powered by the battery.

The conclusion based on this test: the alternator is not completely bad, but intermittent bad. Is that right? Is the method reliable?

 

[DanW]

Not sure but it sounds like a bad voltage regulator which is part of the alternator. Not sure why they could not find that out when you had them check it at the auto parts store.

 

[phattyduck]

Not sure but it sounds like a bad voltage regulator which is part of the alternator. Not sure why they could not find that out when you had them check it at the auto parts store.

Load on the test might not be enough to stress the alternator enough. I would guess a bad diode, not regulator (the regulator seems to be working when there isn't much load). That could also explain the parasitic draw.

-Charlie

 

[WiiMaster]

Hondas do have dual stage charging so the drop you're seeing could be low charge mode?