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Discussion Starter #1
I have a 2006 Honda Odyssey (Touring Model) with an electrical issue.

The car was periodically having a “Check Electrical System” warning associated with a chime, but before I could check the voltage with a meter, the apparent low voltage condition would clear. I installed a voltage gauge so that I could monitor voltage while driving. I discovered that voltage was floating between 14.5 and around 11.8 volts. Ultimately, the alternator was replaced.

After the alternator was replaced and a couple of short drives without issue…

Day 1:
I drove the car for 2-1/2 hours or so— on a 120 miles trip with no issues, monitoring the voltage closely which ran around 13.5 the entire drive. I parked the car for roughly 4 hours. Cranked the car and drove it appx. 10 minutes, then got “Check Electrical System” warning again. The voltage dropped for roughly 8 to 10 seconds— to around 12 volts, then returned to 13.5. We stopped to eat about 15 minutes later, so we were parked for maybe 1.5 hours. Cranked the car again, and drove home— another 120 miles. No incidents at all. Voltage remained solid about 13.5.

Day 2:
The following day, I drove the car on another 100+ mile drive on the interstate. It was very nearly the same situation as the day before (though to a different destination). No issues at all for the drive out. I parked the car for a couple of hours, then restarted it. Just like the day before, after roughly 10 minutes of driving, I got the same “Check Electrical System” and for about 10 seconds, voltage dropped to 12, then returned to 13.5-- again just one time. Within about half an hour, we stopped to eat (and with no further voltage drops). After dinner, we cranked the car and drove 100+ miles home without further incident. (Voltage remained stable the whole time.)

Day 3:
I cranked the car and drove about 15 minutes and got the now familiar “Check Electrical System” warning again. Voltage dropped to around 12.0 volts as usual, but this time the car reverted to the old (pre-alternator-replacement) behavior. It was alternating between 12.0 and 13.5 volts. Repeating over and over, there would be roughly 30 seconds or a minute of malfunction then about the same length at 13.5 volts, seeming stable. The time then began to vary from a few moments to several minutes between stable and fluctuating. I ended up stuck in heavy traffic and had to drive for over an hour to return home. Over that hour, the car probably chimed with the warning at least 20 times in that hour, (sometimes re-chiming moments apart, sometimes minutes apart) and the voltage would vary frequently, landing briefly mainly at either 12.0, 12.7, or 13.5 volts.

The alternator was just replaced and the new one seemed to make the old behavior go away, but Day Three’s behavior seems just like the original problem. What could be causing this apart from the alternator (or could be destroying the alternators?) This particular failure mode would seem pretty unusual for an alternator, and I’m not aware of anything in the electrical system, that could cause this sort of behavior. (Unless maybe there is a intermittent connection on the field wire to the alternator? Would that do it?)

I have to get this car working safely. This is our main family car and we drive it on long trips in the summer. It must be reliable...
 

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Discussion Starter #2
Driving this a bit more with the battery now recharged, I think I may have found a slight correlation with the voltage shift following my doing a bit of "slalom" driving. I'm not certain, but it seemed like the voltage shifted two times when I abruptly moved the steering and pulled some "lateral G's"

The problem is it does it plenty when not shifting the car, so that could be a random coincidence, but here is my thought-- Changing the alternator would do two things-- 1) change the alternator in use (obviously), and 2) change the tension on the plug and wires going to the alternator.

My thought is that we ended up with some slack on the alternator plug (or some sort of tension change) and that perhaps as the wires resettled and shifted from heating and cooling and just time, a damaged plug or wire settled back to the old position it had been in, and the old behavior returned.

There is just almost no chance at all that two alternators would behave so similarly.

With stranded wire, as is used in these harnesses, it seems much more likely that something has failed at the end of the harness; at the plug into the alternator. That seems an inexpensive thing to change as well... only how do I find the part number? (If one exists at all.) I don't really want a home-brew solution, and I also would bot care for junkyard attempt, if I can avoid it.

Suggestions? Is there a replacement part number or a quality aftermarket replacement that has the proper retaining clip and high quality contacts?
 

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Could you clarify what was the alternator replaced with? It is not unheard that aftermarket alternators fail right out of the box. It would be nice to know if it was an OEM, aftermarket or rebuilt and what was the origin of the part.

The specification says the charging voltage should be between 13.5 and 15.1 so the voltage you are seeing is on the very low end of the acceptable range. I have just replaced mine about a month ago and when under load the voltage is around 14.2.
 

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The field voltage connector, which is controls alternator output, and is small connector on back of alternator, comes from the van's computer. You might first want to check on a 'good' car, and compare to your van.

Again, others with more direct experience can help. Also, Youtube is your friend!
 

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Discussion Starter #7
Thanks for all the replies. I've been YouTubing and Googling away. Nothing seems to reference a particularly similar problem so far.

The alternator was replaced with the same unit twice-- a remanufactured, "lifetime warranty" unit from Advanced. The first replacement seemed to work fine for a couple of years. I didn't have a gauge to check the voltage while driving attached until I got a couple of warning chimes a few weeks back though, so I cannot speak to the voltage of the unit when first installed. What I **do** know is the car never gave a warning chime once about the voltage for nearly two years. I've replaced more alternators than I'd care to count over the years (dozens) on all kinds of cars, but this (apparent) failure is different--

I had them repeatedly load-test the alternator, and they always said it was charging properly, but no matter how many times I tried, by the time they would get to the car to check it, the voltage would be reading at least very close to 13.5 (their apparent cutoff). I think once I was reading 13.3 but they still showed it passing. After enough checks, they finally agreed to just swap it for me-- I had also provided a video of the voltage jumping all over then stabilizing as I drove.

I'm getting wild fluctuations followed by normal behavior, sometimes for only a few minutes, sometimes after stability for a couple of hours. Fluctuations can be at idle, on city streets, or freeway speed. Smooth straight roads, or bumps and twists. The recent replacement seemed fine out of the box, but was only stable for about 150 miles of driving. Chimed once for a moment, then was stable for another 200+ miles. Chimed again for a moment. Stable again for 120+ miles, then suddenly went to the previous insane behavior of the last alternator.

I'm used to alternators that either just fail, or they become weak and can't quite keep up. This business of random fluctuations then stabilizing, back-and-forth is totally new behavior to me, and having two do this back-to-back seems like a very large coincidence.

The battery appears to be fine. It has yet to even crank slowly, but after the lengthy events of voltage fluctuation, I have topped off the battery as well. Worst case, the charger will read that the battery is down to perhaps a 60 or 70% charge after these incidents, but then again, I generally go straight home when things act up. The worst situation so far has been getting stuck and having to drive for an hour in traffic to get back, and it isn't driving off the battery the whole time, it is charging about half the time, and discharging about half the time (very approximately).

Still, with the initial issues, I let the battery sit, charged, as the car was not used for as much as a week or two, and it always cranked the car fine.

I've been lucky and with each bad phase of alternator behavior, it has been clear and daylight, so I could run with no wipers, no lights, A/C off, stereo off, etc. Yet when seeming to properly charge, I can turn on the A/C, stereo, wipers, seat warmers-- headlights-- entertainment system-- and even at idle, the voltage remains stable and clearly charging.

I have consistently seen both of these alternators start off (cold start) in the low 14's and ramp down to around 13.6 / 13.5, presumably as the battery is topped off from cranking.

The battery was changed with the first alternator change, so it is about two years old, and it is a premium battery, not a cheap one-- I think it is fine. I may change it, just to eliminate any questions, but it has never even cranked slowly. I cannot imagine it has a fault to pull the voltage down to 12 or even 11.8 but will then consistently crank the car, but obviously something is pulling down the voltage at times. It can't just be the gauge-- I've seen it with more than one gauge, plus the car's own warning system, alerts me.
 

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Discussion Starter #8
This is the get-the-kids from school car-- general family use, and that means it is also the vacation car. Summer is coming, and I need this sorted out. We already took two 100+ mile away "Spring Break" trips last week when the odd chimes happened (once each trip, near the destination!) with the new alternator. Had the rapid fluctuations started 100 miles away, I think the story would not have ended without a wrecker hauling us home.

In a couple of months, I need to be able to trust this car for an annual Georgia to New Jersey and back loop, filled with luggage and my whole family.

Changing this alternator is a giant hassle-- noting like all of my older cars & trucks. Access to swap it is terrible. I don't even mind paying a shop to swap this ($150-ish), and if necessary, I'll pay for a new OEM unit and and the labor, but I want some confidence that this is even the problem.

What I *really* don't want it to spend other $400 for parts and labor, and then to get halfway to New Jersey in a month or two, only to discover that the problem is back and I have no local repair support, and no tools or place to work on this car...

I keep hoping this will be a familiar problem someone else has experianced. So far, I haven't heard of anything that seems to match up.

Thanks again for all the advice.
 

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Discussion Starter #9
The field voltage connector, which is controls alternator output, and is small connector on back of alternator, comes from the van's computer. You might first want to check on a 'good' car, and compare to your van.

Again, others with more direct experience can help. Also, Youtube is your friend!

The connector looks and feels fine, but that doesn't mean there's not a marginal internal connection. Yet again, I cannot correlate particular vibration or movement with driving, or anything apart from the fact that when first plugged into the new alternator, things seemed more stable for about 400 or 500 miles.

Now, I cannot recreate the stability (so far) by messing with the plug.

If I have managed to repeat this same failure mode on two alternators in a row, I'm pretty amazed (and discussed). But another thing to ponder is why I had the two chimes at about replacement + 150 miles and replacement + 450 or so miles.

Something just does not add up.
 

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Discussion Starter #10
Could you clarify what was the alternator replaced with? It is not unheard that aftermarket alternators fail right out of the box. It would be nice to know if it was an OEM, aftermarket or rebuilt and what was the origin of the part.

The specification says the charging voltage should be between 13.5 and 15.1 so the voltage you are seeing is on the very low end of the acceptable range. I have just replaced mine about a month ago and when under load the voltage is around 14.2.

I expected around the low 14's, which I see when I crank, but it falls off. I was told that's normal. And since Honda won't give us gauges, I have no way to know what this van did before I added a gauge.

Maybe I just need to cut my losses and pay for an OEM replacement by a mechanic.
 

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Discussion Starter #11
I just learned of some additional possible causes. I'm an old school guy. My brain works with 1970's Chevys & Fords. New cars have so many variables.

Chief possible issue now sounds like a Load Detection Module for the electrical system, specifically called an ELD, or "Electronic Detection Module". Has anyone had one of those fail?

The trick is going to be getting the car to misbehave for a mechanic, vs randomly swapping parts to see what solves this.
 

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These charging systems are not the systems from our old Chevy pickups. They are PCM controlled. That means it uses an Electronic Load Detector (ELD) and the PCM reduces the output of the alternator based on detected demand/load. This is to reduce emissions and get better fuel economy. Below is a wiring diagram of how it's connected. I've never test an ELD to find out what it's supposed to do but it's a bit rare for them to fail on these vans. If they do, it means replacement of the entire underhood fuse/relay box as it's built in. Other Honda vehicles have replaceable ELD's but supposedly this one isn't replaceable.

I would suspect low quality rebuilt alternators with bad regulators or brushes first. When I replaced mine I bought a brand new one right from Honda. It cost a lot but removed most of the likelihood of being junk out of the box. It's not a job I wanted to do twice. I would also check all the battery terminals and connections, as well as your ground connections. Also, check the connection from the back of the alternator, going to the underhood fuse box, through the 120A fuse, and then to the battery. That connection to the 120A fuse is made on the driver's side of the underhood fuse box with two philips screws.
 

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Discussion Starter #13
Thanks, I'll check it over, but I'm about ready to just take it to a repair shop. My motivation on the rebuilt alternator was it had a lifetime warranty, and as I keep cars forever, those have traditionally come in handy. I've also had places like Midas replacing brakes & mufflers again and again on the same cars for 20 years or more.

The replacement alternator was actually the most expensive one at the parts house that fit. I also absolutely HATE our local Honda dealership. They are a nasty place to deal with. Overpriced, deceitful, and pushy. After our last Honda was totaled, I went and test-drove a new one. I was seriously thinking of just buying new right up until the pushy sales manager said I "needed to be ready to pull the trigger" and buy after the test drive. At that point, there's nothing on the planet that would have gotten me to buy a car from them. So this means that I have to drive a LONG way to get to a local dealer, or I have to mail-order parts. Hence buying at the parts store. Live and learn, though again, I'm not at all convinced that is the problem anymore.

Having changed so many alternators over the years, I had no idea what I was getting into with the half-millimeter clearance to get the old one out and the new one in. I just don't have the time and patience I used to have to repair things myself... I figured this would be an hour swap. It took a couple of long afternoons.

The latest alternator's behavior is so similar to the one which I had assumed failed, that I expect this alternator is okay-- that they both must be-- particularly given that the replacement seems to run okay for extended periods of time, and it seems to run well then stop, back and forth.

With a freshly charged battery over a test drive today lasting just under an hour, the voltage dropped into the 12.5 volt and below range at least 55 times that I could count, sometimes for a moment, and sometimes for a minute or more. I probably missed some, but I have a gauge temporarily in a position that I can see easily, just under the rear-view mirror. Then it would hop back up to 13.5 or more.

The voltages I observe at this point are pretty random between 14 or 14.2 and around 11.8, but the trend drops downward as I drive, so initially 12.5 to 14.2, and later hopping more between 11.8 and 13.5. It also took 5 minutes from a cold start to begin acting up. I lost count of the chimes, but the voltage dropped enough to trip the warning display and chime probably 25 or 30 times, and most of the time, was on long enough (or dropped severely enough) that the little battery light lit up as well. (This is a touring model, so the information center can also display the "check electrical system" warning, written out.)

I still have a Chevy pickup. At times like this, I like it better than my Honda, but for some reason, the family doesn't want to bounce along in a truck so much... I actually think I want my '62 Chevy Impala back. I miss the good old days...
 

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Here are the relevant pages from the SM if you decide to do a thorough troubleshooting. It does not look that complicated. You can get a basic multimeter in Harborfreight for $6 and sometimes they give them away for free if you buy something at their store.
Please report back if you find the problem but my guess at this point is that you have a bad voltage regulator or a bad connection from the alternator to the frame or the fuse box.

I replaced mine with a Denso rebuilt (by Denso) one. Drove about 3k since the replacement with no issues so far (knock on wood) :). Good luck!
 

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Driving this a bit more with the battery now recharged, I think I may have found a slight correlation with the voltage shift following my doing a bit of "slalom" driving. I'm not certain, but it seemed like the voltage shifted two times when I abruptly moved the steering and pulled some "lateral G's"
[...]
Suggestions? Is there a replacement part number or a quality aftermarket replacement that has the proper retaining clip and high quality contacts?
Are you sure the belt isn't slipping?
 

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Discussion Starter #17
No belt slippage, tkrotchko, but worth a check.

Thanks for the documents, OdyMember, I will read through those.

I took the car to a local repair shot that I trust. They troubleshoot the car for 4 hours (and declined to charge anything because they could not find a definitive cause) but they shared a good deal of information. This is outside of my experience, being an "old-school" kind of guy, but it sounds reasonable, and the mechanic would have no reason whatsoever to make any of this up-- he said this was not something he can solve and suggested a Honda specialty shop that might help, but seemed to think a Honda Dealership was the best route of all. He's not going to benefit from telling me that-- if anything, it costs him money.

These cars don't just have a field wire that is energized to charge the car like on old alternators. A computer system, senses the charge rate needed and cuts the alternator back, based on demand. Apparently the computer quickly turns the alternator field on an off to alter the voltage produced. That may be common knowledge, but I had no idea...

So the voltage drops which I'm seeing are apparently normal, or at least closer to normal. This is why replacing the alternator produced no meaningful change. Still, the warning alarm should not be sounding.

What was apparently causing the voltage to drop more of the time is (rather ironically) the fact that I have turned OFF all my accessories. Since I'm not drawing as much power, the alternator is frequently going to a reduced power mode. I will test drive it more today and load things more heavily (electrically speaking).

To be clear, the car is periodically alerting me to a low charge situation still, and that should not be happening, so something is still amiss. Yet the car, so far, seems to run fine and starts fine. The battery, incidentally checks out to be above the factory specs slightly and has never appeared to be getting low.

Another big factor adding concern for me is that when I DID have an alternator failure a couple of years ago I got exactly one warning chime's worth of warning and the car was stalled and dead within about 5 minutes, running with all accessories off.

What I'm hearing from the shop is there is a small chance this could be two bad alternators in a row (after the first replacement worked fine for two years, and even though it was continuing to charge) or the control module (which I understand is built into a fuse box?) or one of a couple of computer modules, or possibly the display panel itself. That's a lot of variables. Replacing everything would most likely fix the problem, and I suspect cost me a grand or two-- not a strong plan. So I'm sort of stuck, for the moment.

Maybe a Honda dealership can solve this, if I can find one around here which is more honest than the nearby dealership.

I took my last Odyssey to the local dealer for a leaking water pump at 97,000 miles. I had just bought the car and didn't know it needed a timing belt 3000 miles later. They replaced the pump and told me (when I picked up the car) that I would need the timing belt serviced in 3K miles. Only when I went to a local shop for the timing belt replacement did I learn that normally both repairs are done because the labor charge for each repair is the same, and if both are done a once it saves all the labor from one of the repairs. That's just bad business-- very dishonest.

Further research revealed this being fairly common practice at this place. Their reputation is not good, and they have exceedingly pushy salespeople as well.
 

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Regardless, you still have a voltage to the alternator field that, in your case, is controlled by the car's computer. In older cars, the field voltage was controlled by a voltage regulator, that was internal to the alternator. If you can monitor that field voltage, while you are driving, that would be a big help.

Also, and unless you have a huge load on your system, a fully charged battery, will not immediately drop below 12 volts, even if the alternator shuts down.

Of note, if you monitor battery voltage while starting your car, the voltage shouldn't drop much below 9 volts. The starter is a very, very large short term load.

Also, the Torque app, for the Android phone, along with a Bluetooth OBDII adapter, total less than $20, can monitor and store alternator voltage while you drive.
 

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Discussion Starter #20
Pappy, thanks-- I'm a little concerned to try this without more information-- what would the result tell me, and what is the risk of running the car this way? I don't want to burn up a computer part, etc.
 
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