It is normal for the voltage to change depending on the load. That's how Honda charging systems work.

 

That was my guess, but that high >16V reading made me think there might be another issue. I read somewhere that can also be a symptom of a bad ELD.

 

Hey,

About a month ago our 2014 Odyssey (123K miles) stalled while my wife was driving. After doing some testing with my voltmeter, it seemed clear that the alternator was going bad. So, I bought a new one and replaced it. This video was incredible:

At the time, there were no Denso alternators to be found online due to supply shortages, so I bought one of the Advance Autoparts ones that everyone warns against, since they will go out after 3 years. I needed the car working ASAP, so that was a reasonable tradeoff.

2 days of driving later, the car stalled again, with the battery light on. So, either 1) the crappy alternator failed immediately, which has been reports, 2) I spilled some power steering fluid on the alternator when re-installing it, or 3) the VTEC oil thing was leaking.

So, I bought a real denso alternator. Yesterday, using MrRangerZr1 videos, I replaced the 2 oil rocker gaskets while I had the alternator out:

Got my battery charged overnight, started it this morning, let it run a few minutes, and the voltage read 14.5 V. I put a voltage meter in the cigarette lighter, and it was reading 13.9-14.1. I let it run a little more, and the voltage measured at the battery was 16-16.5 V, which was strange...

I drove it a little, while watching the internal meter, and it was fine for 5 minutes at 13.9-14 V. Then it suddenly dropped to 12.3-12.5 V. Uh oh. If I turned the air on, or came to a stop, it would jump back to 14.

So, are these jumps normal? Is there another problem? It looks like the Electronic Load Detector might be an issue? Not sure where to go from here.

Thanks!

How old is the battery? Previous alt could have damaged the battery. I don’t like the 16-16.5 volts. That can kill a battery. Was the Denso a rebuilt? Who rebuilt it? Some places do not use genuine Denso parts, like especially the voltage regulator.
A non-Denso alternator has to be looked at as though it came from harbor freight. just like their tools, might work once but just won’t last with heavy duty use.

 

Thanks for all the replies and suggestions. Going in order from the top:



The new one is a rockauto DENSO reman:

More Information for DENSO 2100887

The battery is from Nov 2019, so not too old, not brand new. Maybe I should have it tested?

[EDIT - this all depends on that 16V+ measurement being accurate. So I'd first confirm accuracy of the voltmeter. Measure on a different car, or use a different voltmeter, etc. to confirm]

It MIGHT be the multimeter. I got it in college 20 years ago for my electrical engineering degree. I just tested a 9V battery with a 100 ohm resistor in parallel, and it read just under 9V, so i'm pretty confident it is ok. It measures the battery at rest at 12.5 V, and car running at 14V, which are both reasonable. I haven't seen that jump since the very first test. I'll try again tonight. Also, I read your thread in in depth about the warning light not really mattering. Good info in there.

And its very easy to remove odyssey alternator compared to other vehicles.

The first time I did it took 3 hours, I did it two days ago in 30 minutes. MUCH easier the 2nd time around, mostly because all of the bolts are unjammed!

It is normal for the voltage to change depending on the load. That's how Honda charging systems work.

This was the first response in this thread. I was hoping to get some consensus on this here. Assume my multimeter is busted and the 16V measure was erroneous. Is it ok/normal to see occasional drops to 12.5 V while driving? I'm guessing most people aren't keeping real-time voltage gauges going and monitoring while driving.

I wonder if this was actually a bad alternator to begin with. What are the chances of one alternator going bad, getting a bad replacement, then ANOTHER bad replacement? I guess it COULD be explained if the first one was bad, I screwed up the second one spilling a little fluid on it, which hurt the battery, which is causing issues for the NEW alternator. So, is testing the 2 year old battery the next step?

UPDATE - just did the test again. The battery with car off is 12.7 V, voltage across the battery running is 14.3. I read on another thread that if the battery is fully charged, the alternator may stop charging it. I had the battery plugged in charging overnight with a 2A battery maintainer, so it was FULL this morning. Maybe this explains it?

 

could your volt meter be the issue?

Try another meter and see if the results are the same.

 

If you can repeat the test and it still puts out over 15+ volts, the voltage regulator is not working properly. Do the same test with a new battery and if it still comes out the same, sorry to say, but the voltage regulator in that alternator needs replacing. Your max output should only be 14.5 V. In your case, return the alternator for a new one. Should get a free replacement since you just got it. I had successfully fully rebuilt my 99 alternator-(5 years ago) and I had an issue with one source of voltage regulator then. Finally found one that puts out the correct voltage.

Advance auto alternator has lifetime warranty. You can get a free replacement for the one that failed. At this point, I would try sticking with the longest warranty. IF you did spill oil in the alternator, then that was your error not the alternator. Return the other one for complete refund if still within the time allotted.

 

Advance auto alternator has lifetime warranty. You can get a free replacement for the one that failed. At this point, I would try sticking with the longest warranty. IF you did spill oil in the alternator, then that was your error not the alternator. Return the other one for complete refund if still within the time allotted.

But what is the point in getting another parts store alternator? A Denso alternator is all that should be used.

 

I agree that denso alternator is better but apparently the one he got is not. I believe that not all part store alternator will die fast. Just like not all denso reman alternator will have less issues or last longer. Hence, you better off with longer warranty. Maybe if you are putting a new(2-3x the cost), not a reman denso, then you would expect a longer life. But a reman, who knows what they put in there even if its denso. Just my 2 cents.

 

I do agree with your statement, however lots of experienced techs in the field dealing with comebacks and removing and replacing bad quality reman alternators, is why denso is strongly recommended.

YMMV with all others, and shops that value their reputation always go with the good parts.

 

And its very easy to remove odyssey alternator compared to other vehicles.

 

Says no one
I just replaced the alternator this past week on my '10 EX-L. 2+ hours to get it out, 3+ hours to get the new one installed. I think next time I'll remove the tensioner and washer bottle to do it.

 

Here's a good video on how Honda charging systems work.

 

If you're not having any issues, I wouldn't worry about it, especially now that you've found the multimeter to potentially be suspect.

 

Quick update that I edited my post #15 above since I saw the ELD and ECU drop the charging voltage today, for the first time ever. Details above. Good to know things are working closer to how they are supposed to than I had previously thought.

Short answer conclusion is that the VCM muzzler resistor (77 Ohms) I put in there affects the ECU's control logic for when to switch off the charging.