Last night as I started take my 1996 T4R out on the hwy for a good long run to get ready for a smog inspection, the 4 runner died on me on I-805. Not even any dash board lights, or flashers. A totally dead brand new battery. The State troopers happened along and they were kind enough to push me 200 meters and off the hwy.
This morning I went to Auto Zone and they fully charged the battery , but they said it sounded like an alternator problem. I managed to limp up to Auto Zone and they used some small electronic devise that clamped on the terminals of the battery. I got the runner started and he told me that it was DEFINATELY a bad alternator. How reliable are those devices?
I hate to start changing parts at random, in the hope that one of them is the problem.

Also, it seems that I was running on battery power alone to keep the 4-runner going.

any thoughts or advise greatly appreciated. Thank you.

Alternator brushes are shot. You can get replacement assembly for $20 but probably have to order them. Are you in a position to remove the alternator and remove the brushes to inspect?

Outside chance that the regulator is the culprit, but brushes last to maybe 230k. What’s your mileage?

If it’s an alternator problem, which is likely, you should have had a dash light to indicate the problem for a few hours before it died completely while running on battery reserve.

If it did not indicate alternator fail light then either your light is out or it was a sudden hard fail of some part.

Toyota alternators can be pretty much a lifetime part with brushes periodically changed.

What's the voltage at the battery while the engine is running?

Put a trickle charger on the battery while you are trying to figure this out. No reason to ruin another one while you are figuring this out.

The OEM alternator is very reliable, but the brushes will wear out somewhere north of 150k miles. It'll be good for about the same amount of time again (unless damaged for some other reason, generally) when the shaft will also be worn out.

-Charlie

Agreed. My 2001 died on my wife with little advance warning. Brushes were bad, but nobody carried them, not even dealerships. So I was bent over and had to buy a reman aftermarket alternator. The OEM alternator was mechanically fine otherwise. I knew better, just delayed replacing the brushes and got bit.

My mileage is 195 K

Phattyduck, After the 2 hour charge at Auto Zone, the guy told me that the voltage of the battery with the T4R running at idle was 12.6 volts.
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I do not feel competent enough to change brushes. So, I'll have to have someone else do that job for me. Either that or I'll replace the alternator myself.

I definitely did not see any warning light on the dashboard. But, then again, just before the major problem on the I-805, ALL my dashboard lights went out.
When I got the 2 hour battery charge at Auto Zone even my rear tail lights AND for some very mysterious reason my alarm system, had stopped functioning.

I'll look into buying a reman alternator if I can locate one on the internet.

I’ve got 180K+ on my 02, sounds like the smart move would be to pick up a set of brushes to have on hand in advance of failure.
Anybody have part number & recommendation on where to source them.

A friendly tip: if you can remove your alternator, you can replace the brushes. Its a small assembly held in with two screws, and no wiring to do. Google it. You’re already going to have the alternator in your hands anyway.

Auto Zone has a reman alternator list for $141 +tax.
eBay has some listed for $75 but no info about the part.

I don't suppose that my problem could be something like a voltage regulator or a fusible link ?

Phattyduck, I just received my copy of Haynes Repair Manual and it said, "Start the engine and check the battery voltage. It should now be approximately 13.5- 15.1 volts". Auto Zone claimed it was 12.6

Haynes also said that bad brushes would make a high pitched screeching noise.
I don't hear any noise like that.

What any of this means exactly, I have no idea.

Just checked with Auto Zone. They have alternator brushes that supposedly fit my 1996 T4R

Bad alternator brushes don’t make noise, they just don’t produce power as they are too short to make contact.

I’m not disputing the bad alternator, but if you don’t have a light on the dash indicating alternator problems, then you have more than one problem.

I’m not that familiar with the alternator light circuit. Is it possible the OP could have a blown big alternator fuse/fusible link? That way the alternator is charging so no dash light but the blown fuse cuts the path to the battery? Is this far fetched but possible?

Same story here. A year ago I was coming home from Yosemite. No lights illuminated ever on dash. I started to note the radio cut in and out and with 20 seconds of that I was sitting dead on the freeway. Alternator was my culprit. I've been running fine on the same battery since I got towed and swapped my alternator that day. Changed to a larger alternator since I had planned ( and have now installed) more power drawing accessories on board.

[QUOTE=Traveler74;3515344]My mileage is 195 K

Phattyduck, After the 2 hour charge at Auto Zone, the guy told me that the voltage of the battery with the T4R running at idle was 12.6 volts.
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With a working alternator it would be 13.8 or above in my 4th gen V6

Add one more to this type of failure. I was lucky enough for it to have happened less than a mile from home, but same story. No warning light, and just died. It has been running great for the 6 months since I swapped the alternator.