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Discussion Starter #1
My 2011 Honda Odyssey, 180K miles, has been showing a "Change Batt" indication along with a red battery light. Battery is 6 months old and the alternator has about 50K miles on it. The alternator was installed by a dealership about 2 years ago. The van starts fine. When I check the battery voltage, ignition off, it reads normal to somewhat high, about 13.5 volts. With the ignition on, it reads close to 16V. I took the van to a dealership for troubleshooting and what I got was 1. replace front spool valve. The idea is that it is leaking oil onto the alternator, causing it to fail, 2. replace alternator.

I just replaced the gaskets in the front spool valve and replaced the alternator with a Denso remanufactured alternator from Rock Auto. Voltage problem is the same - nearly 16V with ignition on. The old alternator that I pulled from the van did not have sludge or signs of oil on it. I'm at a loss. Anyone have any ideas?
 

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Carefully inspect the wiring harness in the engine bay. There may be rodent damage, causing incorrect charging voltages.

-Charlie
 

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Discussion Starter #3
Carefully inspect the wiring harness in the engine bay. There may be rodent damage, causing incorrect charging voltages.

-Charlie
Charlie,
thanks for the suggestion. No evidence of rodent damage. No frayed or broken wires that I could see.
 

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13.5 with the key off? something is strange for sure.

did you try a different multimeter, or battery test tool?

I get 14.1-14.5 running 12.5-12.8 key off.
AGM battery.
 

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Discussion Starter #7
I think it's just that high because it's been overcharging whenever the engine is running. I have not tried a different multimeter, but I probably will. I just figured if that was the issue the van wouldn't be giving me a change batt annunciation and a red battery indicator.
 

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it sounds a lot like a bad alternator.
check the alternator output.

is there any warranty from the dealer on this replacement alternator?
 

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Discussion Starter #9
The dealer-installed (reman) alternator was 2.5 years old, but had 50k miles on it, so no warranty. The one I just put in is likely getting returned since I don’t think the alternator I just took out is the culprit. I think the likelihood of 2 alternators having the exact same problem is pretty low. There is something else going on.


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good work on the denso only alternator...
this is the common theme
remans usually fail to produce adequate output.

overcharging is the alternator, and kills the battery along with it.

something is blowing the regulator in your alternator, my guess is the battery.

what kind of battery did you replace the old one with?

are there any electrical mods to the vehicle?
inverters, additional batteries that are running off the charge system?

Also inspect those grounds!
 

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Discussion Starter #11 (Edited)
The battery is a Walmart Everstart, bought is May this year. No other electrical mods to the vehicle. My thought was to chase wires looking for a short, but that’s a little too much for me. It did not occur to me that a battery would mess up the alternator/voltage regulator. The batt voltage was probably 13.8 or so when I cranked it up the first time after installing the alternator.


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Before getting carried away, try with a different meter. You might even stop into an Advance Auto or Autozone and have them check it. I can see having an over charging issue but I don't see any way to have 13.8v on a battery when the engine is off, even with some overcharging. I've never seen that kind of voltage on a battery so your meter is suspect at this point.

You could also try your meter on a different car and see if it's reading high on other cars.
 

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Discussion Starter #14
Before getting carried away, try with a different meter. You might even stop into an Advance Auto or Autozone and have them check it. I can see having an over charging issue but I don't see any way to have 13.8v on a battery when the engine is off, even with some overcharging. I've never seen that kind of voltage on a battery so your meter is suspect at this point.

You could also try your meter on a different car and see if it's reading high on other cars.
Well, that was it. Thank God. I tried the multimeter on a 9V battery and it read somewhere north of 11V. Borrowed a friend's multimeter and it reads 13.8 running, so the alternator I installed is working properly. Still not sure about the previous alternator and what the problem was that caused the "Change Batt." If my meter was reading high the whole time, the voltage was probably normal while the indication was showing. In any case, I'll drive the van around for 30-60 minutes to make sure it doesn't come back.

Thanks for your help. Hopefully this thread helps someone else in the future.
 

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Well, that was it. Thank God. I tried the multimeter on a 9V battery and it read somewhere north of 11V. Borrowed a friend's multimeter and it reads 13.8 running, so the alternator I installed is working properly. Still not sure about the previous alternator and what the problem was that caused the "Change Batt." If my meter was reading high the whole time, the voltage was probably normal while the indication was showing. In any case, I'll drive the van around for 30-60 minutes to make sure it doesn't come back.

Thanks for your help. Hopefully this thread helps someone else in the future.
Throw that meter away and get yourself a new one. Bad/cheap test equipment can actually cost you money, as it did in this case. I use a Fluke DVOM, as well as Snapon Vantage/Vantage Pro just so I can always trust my results. You don't need to spend anywhere close to that kind of money but you definitely want one you can trust.
 

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Discussion Starter #18
Old meter is already in the trash. Drove the van for a good 30 minutes and no change battery indications popped up, so the new alternator did the trick. Really glad I didn’t have my van towed to a dealership to have a tech tell me that there’s no problem!


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What brand was the old meter? HF/pittsburgh?
 

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Discussion Starter #20
It was pretty old. You probably couldn’t buy one if you wanted to.


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