Hello All,

As the title states, I have been getting an intermittent battery light. 5VZ SR5 with 310k miles.

I have a voltmeter in the car and it will go from 14.2-3 to 12.2 to 11.6 back to 14.2. Starts every morning just fine. I did notice that the wipers get slow when the battery light comes on.

My question is, should I just put a new brush kit in the OEM alternator that's in the truck now? Or should I get a generic parts store alternator? Could it be a bad voltage regulator? at 310k I'm sure the brushes are pretty worn out but dont know if that can cause intermittent light. Has never died.

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Get a new brush kit.. the generic alts don't seem to last like the oem or densos do. If you don't wish to do the kit get either from rock auto or a Toyota dealer remfg denso alt. Unless you want to be changing it a pile of times and wasting alot of time with an generic parts store one.

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I have the brush kit (part: 27370-75060) from the Timmy the Toolman video on order and will report back once I have completed the swap.

I agree, if that doesn't work I was looking to get a reman Denso from the dealer or RA.

Just seeing if anyone has had a similar experience that was fixed by the new brush kit.

Deeeeeefinitely want to chime in on this one-- I had the same issue last August. I also second @brillo_76 's suggestions about replacing components/buying reman Denso unit from RockAuto. I had the same exact symptoms as you, and went through the process of replacing the battery first (which needed to happen anyways) and then ended up purchasing a reman Denso from RockAuto. While you're in there, if you do swap alternators, change the belts too since you'll have easy access to them, and they're cheap. But I've had great results (knock on wood) thus far with my reman Denso unit. Also, I purchased the reman alternator on a Tuesday at 11 AM, and it literally arrived the next morning by 0900. Paid for regular shipping, too. Pretty dope IMO. Best of luck!

Awesome! I will report once I have the new part installed!

Thank you for chiming in.

Lots of people rebuild their alternators. I plan to rebuild a few here down the road I haven't done any yet.

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I think you're on the right track by changing out the brushes. Super easy to do. Here's a picture of a set of brushes with 280,000miles next to a new set of brushes. I can hardly believe they were still working fine when I changed them out as a routine maintenance item. I seriously doubt they would have lasted another 30,000miles. So yeah, at 310,000miles you are due.

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A new brush kit should get you another couple hundred thousand miles... then you can get a reman Denso for the new bearings, etc. since the shaft will likely be pretty worn by then.

-Charlie

Oh yeah, I forgot to mention this, too. And I'll quote @brillo_76 once again, SAVE your old alternator, especially if it's an OEM one. Even if you don't have the tools, parts or otherwise resources to rebuild it right away, I think you should hang onto it for that purpose alone so you can carry as a spare and/or install it back once the newer one goes out. That's what I ended up doing with my old one, although I forfeited the $30~ core fee from RockAuto. Which is fine. But I have every intent to rebuild it in the future, as it would be cool to learn something new

I picked up new brushes on my last parts order from Conicelli Toyota.
Threw them in the glovebox until I have some time to pull the alternator.
Figured with just over 200K on the odometer it’s just a matter of time before the need to replace them arises…..same goes for the starter.
That rebuild kit keeps the alternator brushes company in the glovebox.

I had the intermittent battery light, too, became chronic

Went to the junkyard, pulled an alternator, had it tested at parts store. Good.
Threw it in. Good

Took old alt to parts store for grins and giggles. Also good.
Scratched my head and put it on the shelf

2 weeks later, battery light again...

Long story short. My alternator plug on the engine harness was gunked up and not clicking into the alt, working itself loose.

Cleaned the plug out real well. Cleaned alt terminals real well.
Installed plug, tapped it home with a wooden dowel and mini ball peen hammer.
Been fine ever since.

Eventually I will need to replace brushes and bearings, no one is immune from that.

Check the plug, too

When I bought the 97 SR5 project it had a reman CarQuest 80a Alt in it. I put it in the 97 Limited Puppy Hauler when it’s 70a Alt’s diode block went bad. 30k later the cheep reman brushed wore out. (Just nubbies sticking out of the brush housing).

Put a set of OEM brushed in it. Remans are still factory Denso Alts. Just went through the reman bench.


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Holy crap! Yeah the Tim the Toolmans brushes were pretty worn on his video.

Question: If it was the voltage regulator, could it also be intermittent like this or would it just crap out altogether?

I checked the connector on the back and it clicks in well and didnt look to have any corrosion. Will report back once I get the part installed.

You can test the voltage out put of the alternator by checking the battery voltage at idle which should be over 12.4 volts and then reving the engine to 1500 rpms, the voltage should jump up by at least 2 volts. A good charging range is between 13.4 to 14.8.
Also another option, is to take the alternator to a big box auto parts store and have them test it.

Ive done this, 14.3 consistently, but when the light comes on it will range from 12.2 to 11.6ish then will go away on its own.