Alternator intermittently charging, 06 Honda Oddy

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After a battery replacement on my 2006 Honda Odyssey, I have an intermittent battery light on the dash indicating the alternator isn't charging. I confirmed this with a multimeter. However the strangest part is that the alternator works completely fine when the headlights are on.

I suspect an alternator that is starting to fail, but I have never seen behavior like this from an electrical system.

The alternator is a royal pain to change and due to this I will use a Honda replacement, for the hopes of never having to change it again. Currently there is a WPS (World Power Systems), chinese made alternator on it that is 3 years old and the new battery is an Autocraft Platinum AGM. Hopefully it is not the AGM battery causing these issues. I am perplexed.

Anyone ever see conditions where the alternator works fine with the headlights on but works intermittently with them off?

I have tried turning other loads on like the heated seats, etc. and the problem still exist. So I am still running the vehicle, but with the headlights on 100% time.

-Dave
 
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It sounds to me like the brushes have probably had it. I saw this on an 05 with about 100K on it.
Before condemning it take it off and have it tested fro free at AZ or AA. OEM can be really expensive, you might find a a Denso or Bosch for less on Rock auto.
If there is a rebuilder near you this is a good route as suggested. Unfortunately nothing near me.
 
My concern is when tested it may show GOOD since it is an intermittent problem. Also I believe it is hit or miss with rebuilds/re manufactured alternators. Since it is such a pain to change I am willing to pay $295 from majestic honda online vs. that of ~140 from rock auto or a rebuild. I just have never experienced this type of behavior of working fine with lights on, but otherwise intermittent.
 
They should be able to rap the back of the case and get some sort of fluctuation in it. It could be a regulator or diode going out also but these part are usually a hard fail.
Nothing wrong with going OEM but it would be a shame to can it for bad brushes. Personally i would open the case and look at the brushes.

Nothing difficult with this job. It will look something like this.

http://www.ebay.com/itm/ALTERNATOR-Regul...=item46223f5520
 
Originally Posted By: zfasts03
Currently there is a WPS (World Power Systems), chinese made alternator on it

Uh-oh. Aftermarket alternator. Bad juju...

Is the Check Engine light on? Are there any codes stored?

Do you get the same no-charge problem with the headlights OFF and the A/C compressor engaged?
 
Alternators, unlike generators, require excitation current on start up, but once the alternator starts putting out current, shouldn't the process be continuous until shut-down? I vaguely remember a test stand set up that demonstrated that an alternator could be excited with a couple of flashlight batteries. Once the external excitation was removed, the alternator continued to supply current.This was forty some years ago, so I may be wrong.
 
The excitation needs to get to the rotor by way of the brushes. The output is then regulated by changing the excitation current.
 
Just replaced the alternator in my Accord last weekend. Bought a Remy rebuilt from rockauto for about 110 but with an 80 dollar core charge. Some alternators on ebay go for about $45, was tempted but resisted. The Accord's alternator is not difficult - easy access - so going with a dirt cheap alternator was a chance I thought about. But in the end I went with rockauto.

Accord was throwing a P1381, cylinder position intermittent error code. So far so good but it's only about 3 days of commuting.
 
Replacing the alternator will probably not solve the problem. The alternators on Hondas (and many other cars) are controlled by the main computer which regulates its output. There is a Honda TSB and warranty extension for this EXACT problem. A Honda dealer will flash the computer with an update which should take care of the problem.
 
The Honda TSB that I mentioned does not apply to the Odyssey, sorry. But, the main computer DOES control the alternator's output (this could explain why turning the headlights on is doing what it is doing), so an intermittent charging problem STILL could be caused by a computer glitch or computer-to-alternator wiring/connection problem.
 
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103,000, but only about 25,000 on the WPS (World Power Systems), chinese made alternator that is currently in it.

What are the chances it is the computer and not the alternator?

Grounds seem good at least the ones I can find. Also did a wiggle test of the wiring.
 
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Originally Posted By: zfasts03
103,000, but only about 25,000 on the WPS (World Power Systems), chinese made alternator that is currently in it.

Uh-oh. Aftermarket alternator. Bad juju...

Is the Check Engine light on? Are there any codes stored?

Do you get the same no-charge problem with the headlights OFF and the A/C compressor engaged?
 
No check engine light. No codes with obd2 scan tool. I will try running the AC compressor tomorrow with no headlights and see if this makes a difference like the headlight do.

I have been driving the car and 100% of the time with the headlights on the alternator charges fine. Within a minute of turning the headlights off, the alternator stops charging and intermittently will charge again, usually with added throttle.

I have the original alternator that I pulled off a few years ago, due to making a growning noise under load and then eventually shorted completely and drained the battery down to zero. I am going to have this original honda alternator rebuilt and put this on and hope it is not the computer or something else.
 
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Update:
Using either the headlights or the air conditioning prevents that problem from occurring. So as long as either or both are running the alternator charges the battery.

Is it possible that the new AGM battery is causing the issue? Prior batteries have been tradition lead acid.

I am now thinking just drive it as is and run the headlights or AC until I know the definite issue before putting more $$$ or time in it.

Thanks everyone for you input. I am just puzzled!!!
 
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Originally Posted By: zfasts03
Update:
Using either the headlights or the air conditioning prevents that problem from occurring. So as long as either or both are running the alternator charges the battery.

The culprit may be the Chinese alternator not playing nice with the ECM. It's sounding like the alternator cannot operate correctly under Honda's dual-mode charging instructions from the ECM.

Honda uses a dual-mode charging scheme that has a low-charge mode (12.4-12.9 VDC) and a high-charge mode (14.4-14.9). The ECM uses the signals from the Electrical Load Detector (ELD) and other sensors to direct the alternator to switch between modes. This setup is working correctly on your car, as evidenced by the fact that the alternator does switch to high-mode when any sort of heavy electrical load is applied. This is why I had you try the A/C.

I suspect that your Chinese alternator is either not capable of low-charge mode, or that the output voltage in low-charge mode is below 12.4V; so the ECM therefore thinks that no charging is occurring and illuminates the battery light.

It may just be coincidence that the problem started just after your new battery was installed. Or does your AGM battery maybe have characteristics that make it unsuitable for use with a dual-mode charging system?
 
Wouldn't a problem in this circuit set a DTC?
Your right. I completely missed the part that it has a Chinese alternator already. I understood he didn't want one and just wanted OEM.
 
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