[Juggawut]

So today, as driving normally, my battery light came on. I pulled over and plugged in my scanner and it was only pulling 10v while running. Obviously the alternator stopped. Battery checked out fine, but died very shortly after, as expected. I opened the hood and the amount of heat coming from the alternator probably could have cooked eggs if it was a griddle. The smell was horrible electrical burning. I sat for an hour total, including having someone charge me for about 15 mins so I could make it somewhere. I touched the alternator at this point, which had not been running for an hour, and literally burned my finger. I got on the road and drove for the 6 miles to a family member's home. The last mile of the drive I started watching the voltage and it was in an entirely normal range. I parked and left the van running, opened the hood and, more carefully this time, touched the alternator. It was still hot, but cooling. The readings were normal. I drove the half hour home, family member behind me, and the readings remained normal the entire drive. By the time I got home the alternator was at a normal operating temperature.

If everything has gone back to normal, why did the battery light never turn off? It's still on if I go start the van right now. Does the Ody instinctively know that something is somehow still wonky?

 

[hpark21]

I think some type of codes doesn't go away even after the thing that caused the code to pop goes away and needs to be manually cleared.

 

[WiiMaster]

IIRC, the battery light is triggered by a switch inside the alternator. Who knows what could have been damaged with the heat?

 

[geotek]

So today, as driving normally, my battery light came on. I pulled over and plugged in my scanner and it was only pulling 10v while running. Obviously the alternator stopped. Battery checked out fine, but died very shortly after, as expected. I opened the hood and the amount of heat coming from the alternator probably could have cooked eggs if it was a griddle. The smell was horrible electrical burning. I sat for an hour total, including having someone charge me for about 15 mins so I could make it somewhere. I touched the alternator at this point, which had not been running for an hour, and literally burned my finger. I got on the road and drove for the 6 miles to a family member's home. The last mile of the drive I started watching the voltage and it was in an entirely normal range. I parked and left the van running, opened the hood and, more carefully this time, touched the alternator. It was still hot, but cooling. The readings were normal. I drove the half hour home, family member behind me, and the readings remained normal the entire drive. By the time I got home the alternator was at a normal operating temperature.

If everything has gone back to normal, why did the battery light never turn off? It's still on if I go start the van right now. Does the Ody instinctively know that something is somehow still wonky?

The battery light is turned on by the regulator in the alternator. When the voltage is missing the pin goes low to turn on the light. You saw 10 volts output which I think was caused by a shorted cell in the battery. You let it cool off and charged it possibly clearing the short. Now if everything seems ok and the light is still on the regulator is probably damaged. So you are on borrowed time. Changing the regulator might fix the light problem, but I would not trust the alternator not to fail in the future. The heat has stressed all the components in the alternator and diodes or even the brushes might fail. If the battery is 5 years old replace it, if not load test it to see if it still has capacity.

 

[jiantao]

I've heard of the alternator smoking to its death on this forum before. How many miles do you have on your Odyssey and is it on the original alternator?

 

[Juggawut]

I've heard of the alternator smoking to its death on this forum before. How many miles do you have on your Odyssey and is it on the original alternator?

About 140k, 2009 EX. Most definitely the original alternator.

However...

The overheating was most likely caused by a couple load resistors I added to my daytime running lights. I unhooked them as a precaution.

 

[thscott]

Seems like you need a new alternator. Be sure to get a Denso brand. Nothing else.

 

[Juggawut]

What's the importance of denso brand? I mean I know they are OE and I was looking at a remanned "NipponDenso equipped" auto zone branded (duralast) alternator. Is this a remanned Denso? Do I want a remanned denso?

 

[WiiMaster]

What's the importance of denso brand? I mean I know they are OE and I was looking at a remanned "NipponDenso equipped" auto zone branded (duralast) alternator. Is this a remanned Denso? Do I want a remanned denso?

Very important. Get the one from RockAuto. The alternators you find at the parts stores are junk.

 

[Juggawut]

Very important. Get the one from RockAuto. The alternators you find at the parts stores are junk.

Sadly, Rock Auto doesn't have a new one, and I've been having a hard time finding a new one anywhere.

Is a remanned Denso better than no Denso?

 

[thscott]

What's the importance of denso brand? I mean I know they are OE and I was looking at a remanned "NipponDenso equipped" auto zone branded (duralast) alternator. Is this a remanned Denso? Do I want a remanned denso?

What's the importance of denso brand? I mean I know they are OE and I was looking at a remanned "NipponDenso equipped" auto zone branded (duralast) alternator. Is this a remanned Denso? Do I want a remanned denso?

No other aftermarket brand alternator will work very well or for very long - especially the junk Duralast crap sold at Auto Zone.

As said, get a remanufactued Denso unit from Rock Auto. Auto Zone may be able to get you a genuine Denso alternator as well - but it would not be Duralast branded.

 

[thscott]

Sadly, Rock Auto doesn't have a new one, and I've been having a hard time finding a new one anywhere.

Is a remanned Denso better than no Denso?

Remanufactured Denso is what most knowledgeable people here buy.

 

[0dyfamily]

Autoplicity sold me a reman'd Denso that they advertised as new. Needed the car, didn't have time to go through the whole RMA process, so I installed it.

Short answer: Denso alternator reman'd by Denso operates, and is durable.

The foil decal with red lettering said it was remanufactured by Denso (the original mfgr).

I've seen a number of reman'd alternators from Autozone and other chain stores, and they all looked "different". What I mean by that is the cases were crudely sandblasted, patina of silver gray paint on the aluminum sometimes, and well, they sure did not look like they were once an OEM part at some point in time.

The "Remanufactured by Denso" part I received look like a brand new Denso alternator. If the decal was not on it, I would not have been able to tell the difference.

I would get another one for any of our vehicles. With four kids (all driving), a vehicle for me and Missus, and one spare, I would put a Denso alternator (Reman'd by Denso) in any one of them without pause.

OF

 

[marvinstockman]

An alternator will put out lots of volts, say 18+, if it gets an incorrect signal from the computer. And at the same time, it will get hot.

I'd get the below plug in voltmeter, and monitor voltage while driving. If you get a voltage spike, and to prevent further damage, turn on everything you can, lights, fans, rear defroster, etc.

https://www.amazon.com/Jebsens-Charger-Battery-Monitor-Voltage/dp/B01N00I4TM/ref=sr_1_7?dchild=1&keywords=usb+voltmeter&qid=1617456384&sr=8-7

 

[Juggawut]

The voltages are completely normal now. I've been graphing them so I can look for drops but I've got nothing but normal performance. The battery light just stays on anyway.

The alternator appears healthy at this point. The suspected culprit, the load resistors, have been unplugged. Today I plan to run the van for 15 minutes to warm it up, then take temp on the alternator housing with a meat thermometer. Then I will reattach the load resistors and watch for voltage or temperature changes.

Is there anything else I should be watching?

 

[WiiMaster]

Sadly, Rock Auto doesn't have a new one, and I've been having a hard time finding a new one anywhere.

Is a remanned Denso better than no Denso?

You don't need a new one. A remanufactured one is perfectly fine, as long as it's remanufactured by Denso.

 

[thscott]

I’m no alternator expert, but I would not think your alternator is fine. It experienced a massive traumatic overheating event. Either caused by the alternator itself or perhaps an external load.
In either case, I recommend you stay on the path to replace the alternator with a Denso remanufactured unit.

 

[Juggawut]

I’m no alternator expert, but I would not think your alternator is fine. It experienced a massive traumatic overheating event. Either caused by the alternator itself or perhaps an external load.
In either case, I recommend you stay on the path to replace the alternator with a Denso remanufactured unit.

Don't worry, that's the final goal. Right now I'm trying to duplicate the overheating so I can eliminate it if it's external before dropping a new one in.

 

[marvinstockman]

As I suggested, you need to monitor voltages while driving, and not only while idling.

 

[Juggawut]

As I suggested, you need to monitor voltages while driving, and not only while idling.

I have, no change. Optimal performance.

It's hanging between 140f and 160f while idling plugging the load resistors in makes no change in voltage or temperature. It's been running for an hour and a half now.