you positive its not the rectifier?

not replaceable on these, cant even find a part number for them.

 

Did you try local parts stores? My local Napa has Denso reman on hand for $280+85 core. Not available to ship…

What about Honda dealer? Looks like $400 for Denso reman.

I have had ok luck with Carid. I think my parts got fufilled directly from Aisin warehouse, did take them a few days to get correct tracking number, but parts arrived same week.

 

I haven't tried any stores yet, I will be giving that a shot on Monday. It could be the rectifier, but I wanted to eliminate a variable with the brushes as that seems to be a common cause, now that I have them out, the worn and rough split ring is likely the culprit.

Not a big fan of Carid. I ordered shocks, rotors, and pads about 5 months ago. VERY slow shipping, multiple boxes from multiple shippers/suppliers. I called when I received less than 1/2 of my order, Carid aka "Paul" from Pakistan 'assured' me it was delivered, I asked how he knew, 'because FedEx said so', ha. After many calls and emails, they slowly trickled my parts in for the next 6 weeks. Only after multiple follow up calls. They literally 'closed' my case when I was stilled owed most of my already paid for stuff.

 

"slip rings" not "split rings"

It is normal for one to wear faster than the other, due to the polarity of the current flow.

On these alternators replacing the slip rings is so much more difficult and likely to fail than anything else that, it is often not done. Being a rebuild, they probably replaced brushes, and the slip rings just continued to wear.

They can wear pretty far, and a deep groove can be OK. The problem is when you wear all the way through that, into the plastic below. At some point, you just can't get the field current supplied, and no charging will occur.

You might be able to find specs on minimum slip ring diameter. But until you find that, I'll say that as long as you are not yet seeing holes (patches of plastic showing through) in the copper, you probably have more meat left there than you think.

Couple of months or more might be OK. But it would help if you had a better understanding of why one brush wore so much faster than the other. The slip rings should be smooth. So for example, don't file or sand them. I use scotchbrite to make them shiny and smooth. Any roughness due to sandpaper would quickly cut through the brush.

 

One of the slip rings is badly eroded, if the diameter of the shaft is about 15mm, the end ring is 15mm and smooth copper, the inner/lower ring is probably only 10mm diameter and rough, like drag your finger across sidewalk rough. My concern is if I were to reuse this alternator, even for only a short period, the roughness of the bad ring may cause uneven voltage and/or spikes ruining other parts of the system.

 

The roughness of the lower ring is what ate away that brush so quickly. Yes, if you jut put a new brush in there, it will get eaten away quickly.

So you need to smooth out that lower ring. Scotchbrite (the green scratchy stuff on sponges, for example) will smooth + polish it to a good level. But if the copper has already worn all the way through (and 10mm vs. 15mm may be what happened) in patches, game is over. You should be able to clean it up and tell - if you can get the copper smooth and continuous, a couple of months might work. If not, no chance.

I actually would not be so concerned about voltage spikes with this problem. When the circuit goes open due to a problem at the slip ring to brush interface, it means you lose the DC current (of a few amps, like 4 A) that energizes the rotating field. When you lose that, the induced current in the stator winding will be reduced or stopped, but the voltage will just reduce, and it is connected to the battery, so any change in system voltage will be damped by that.

I quickly looked up the specs in the service manual for the slip rings. Hmmm
||| New ||| Service limit
Slip ring O.D. ||| 14.4 mm (0.567 in) ||| 14.0 mm (0.551 in)
Brush length ||| 10.5 mm (0.413 in) ||| 1.5 mm (0.059 in)

I can't say I fully believe that high service limit on the slip ring OD.

Here's a pic of the slip rings in my old Lexus' Denso alternator and the new ones I replaced them with. NOT an easy job. You can see how the top ring is worn much deeper than the lower one. It's a polarity thing, depending on which way the current flows, so apparently yours is opposite this one. You can see the brown plastic substrate showing through the copper as it has worn all the way through. Thing to remember is that the alternator was WORKING up until this point, even with much of the surface area of the upper slip ring gone.

 

The roughness of the lower ring is what ate away that brush so quickly. Yes, if you jut put a new brush in there, it will get eaten away quickly.

So you need to smooth out that lower ring. Scotchbrite (the green scratchy stuff on sponges, for example) will smooth + polish it to a good level. But if the copper has already worn all the way through (and 10mm vs. 15mm may be what happened) in patches, game is over. You should be able to clean it up and tell - if you can get the copper smooth and continuous, a couple of months might work. If not, no chance.

I actually would not be so concerned about voltage spikes with this problem. When the circuit goes open due to a problem at the slip ring to brush interface, it means you lose the DC current (of a few amps, like 4 A) that energizes the rotating field. When you lose that, the induced current in the stator winding will be reduced or stopped, but the voltage will just reduce, and it is connected to the battery, so any change in system voltage will be damped by that.

I quickly looked up the specs in the service manual for the slip rings. Hmmm
||| New ||| Service limit
Slip ring O.D. ||| 14.4 mm (0.567 in) ||| 14.0 mm (0.551 in)
Brush length ||| 10.5 mm (0.413 in) ||| 1.5 mm (0.059 in)

I can't say I fully believe that high service limit on the slip ring OD.

Here's a pic of the slip rings in my old Lexus' Denso alternator and the new ones I replaced them with. NOT an easy job. You can see how the top ring is worn much deeper than the lower one. It's a polarity thing, depending on which way the current flows, so apparently yours is opposite this one. You can see the brown plastic substrate showing through the copper as it has worn all the way through. Thing to remember is that the alternator was WORKING up until this point, even with much of the surface area of the upper slip ring gone.
View attachment 168490
View attachment 168491

Thanks for hte additional pix and info. Based upon what you posted, I assume I am through the copper and into the substrate, oddly enough, the upper, or ring closest to the tip is about perfect, I mean no wear at all. This pic is not mine, just a pic I pulled off the web, but my upper ring is in at least as good of shape if not better, and this lower ring is still in better shape than mine.

 

Another question, I am thinking about a used one from 'junkyard'. Is this type of wear common; in other words should I be concerned about buying another alternator in the 100k+ mileage range knowing I would at least change the brushes.

Lastly, how hard is it to change the rings? I read a thread on the Lexus site and it looked pretty 'tedious' and I'm not sure I want to go through all that for a spare alt.

 

Alternator failure is pretty common after 100k. Especially on this gen where a good chunk of them have been baptized by spool valve oil.

 

One more question...OK. 2.

Do other vehicles in the Honda line using this motor and alternator suffer the same oil leak/alternator issue. It seems the Passport and odyssey share this combination.

Secondly, does the oil leak issue contribute to the degradation of the slip rings?

 

Do other vehicles in the Honda line using this motor and alternator suffer the same oil leak/alternator issue. It seems the Passport and odyssey share this combination.

This is an issue on all VCM-2 engines. I know the 08-10 EX-L and Touring have it, all 11-17, and 2008-12 Accord V6s (except the manual V6 coupe). There are others that have it as well.

 

Continuing saga. I went to the local LQK as they had one for $100 ndn only 102k. I place my core on the counter (It looks like it just came out of the box, clean and shiny), and he places a rusty, corroded piece alt. on the counter, this thing was bad...

Also not a Denso, aaaaand the bearings were clicking, aaaaaaand rebuilt at least once. So I will take my chances at Carid and order a reman Denso.

On the other hand some good news. The batteries on my Titan XD (diesel) are going out and the dealer stated they are covered under the 100k warranty, go figure.

 

Friendly Reminder: Always charge your battery all the way before starting the engine with the new/rebuilt alternator. Don't rely on the alternator to charge a dead battery (unless you're getting an emergency jump start and you're going to be driving fast enough to keep things cool).

Don't ask me why I know how important this is...

 

yeah, have u had battery overheat as a result? I think that's what parts store told me was a risk when i had to replace alt. during weekend trip.

 

Good things to know. I have the battery on a charger while waiting for the alt.

 

Final update: I was a little leery of a CarID.com alt as I don't really like them but they seem to be one of the only places that had it at a good price - time to roll the dice...

It finally arrived several days late and I was on 'chat' to CS quite some time getting a refund of the expedited shipping I paid for, and finally got it. Once I opened the box I was pleasantly surprised, it was a very nice Denso alternator, it looked factory new (I was afraid it was a 3rd party reman of a Denso alt).

I opened up the back of the alt to look at the condition of the slip rings and other than the interior ring being a little tarnished they were pretty perfect. Considering my last reman only lasted about 30k I was worried about the slip rings, but these looked like they will run many 10's of thousands of miles.

Having said all that, CarID conveniently 'forgot' to include any papers, instructions, or return slip for the core. So I had to have them get me the info so I could get my $70 back (I bet they make a lot of money that way). Now off to check my axle thread, come on over and check it out! 😁

 

Final update: I was a little leery of a CarID.com alt as I don't really like them but they seem to be one of the only places that had it at a good price - time to roll the dice...

It finally arrived several days late and I was on 'chat' to CS quite some time getting a refund of the expedited shipping I paid for, and finally got it. Once I opened the box I was pleasantly surprised, it was a very nice Denso alternator, it looked factory new (I was afraid it was a 3rd party reman of a Denso alt).

I opened up the back of the alt to look at the condition of the slip rings and other than the interior ring being a little tarnished they were pretty perfect. Considering my last reman only lasted about 30k I was worried about the slip rings, but these looked like they will run many 10's of thousands of miles.

Having said all that, CarID conveniently 'forgot' to include any papers, instructions, or return slip for the core. So I had to have them get me the info so I could get my $70 back (I bet they make a lot of money that way). Now off to check my axle thread, come on over and check it out! 😁

Are you sure about looking on Rockauto? got a Denso Reman Alt from them in May for a spare, and it came within a few days. Someone here also had problem locating one from Rockauto until I pointed it out so maybe you guys suffered the same symptom. Rockauto list their Denso alternators for non VCM and with VCM in different spot so be sure you scan thru the entire page for alternators.

I had the same experience with CarID and had to call and ask them for return label.

 

First, We don’t have to filter VCM vs non-VCM parts since there isn’t a non-VCM gen4. Previous gen comment above.

Second, It’s not just you. Just pulled up the catalog and it’s not listed. Last time this topic came up I could only find it on RockAuto searching by the part number another member @Ted mentioned

DENSO 2100766 Alternator / Generator | Shop Now at RockAuto

DENSO Electrical Parts and More for Your Vehicle at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

I haven’t verified this is the right part for gen4 Ody. Recommend anyone verify that first before buying the one linked above.

 

There seems to be an issue with Rock's copy of the catalog. Denso shows 210-0766 as the part, and Rock shows it in stock. Normally, if it doesn't come up in a vehicle search, it means the part is OOS.
Confirm P/N at densoautoparts.com.