lights/power/voltage drops

[Previologist]

Good grief. I had it tested with the 93 brushes at the first place, that I trust a lot more than the 2nd (the 2nd being Oreilly). It tested at 13.2, scarcely better than with the old brushes. So is this true variation, or just a freak thing? I have tested it at several points and came up with similar variation. I don't know if brushes could be responsible for this or not.

So now I am thinking a remanufactured Denso may be my best way out of this, but they are a bit too spendy for me at the moment. I may have no choice but to try new brushes, at least they are cheap and I can always use them on my 4runner if I buy a reman.

[samstrader]

When I test my alternator, I put a volt meter across the battery with the car off and I get 12.7 volts. Then I start the car and with the car running, I get 14.4 volts. The higher voltage, in the 14 volt range, with the car running is how I know the alternator is putting out. I got 14.3 volts testing this way with my old and original alternator and 14.4 with my new (rebuilt) alternator.

I don't know how they are testing your alternator but just putting up a little over 13 volts is not enough I don't think.

I may not understand right but it sounds like you have the same alternator in the car with used brushes from another alternator installed. If this is the case, I wonder if the voltage regulator in your alternator is bad or if something else other than the brushes is bad. It should be putting up 14 plus volts. At least that is what my car has always put up and I have checked it many times.

There is voltage loss in the wire going from your electrical system to your headlights. If my car is running 14.4 volts, the voltage at my headlights is a little less that 13 volts when the lights are on. I think this is normal.

[Previologist]

I only switched the brushes this past weekend for testing. These tests over the last few days have all been bench tests under load, although I now wonder whether the test at Oreilly was actually under load or not. I do not trust their employees to know what they are doing. But they are similar to what I have seen testing across the battery. Technically even the worst result should still be adequate for charging the battery though, but I want to see it test over 14 on the bench with no load and be certain it can stay over 13.5 under load before I even bother putting it back in. Its a pain in the butt to get in and out of a 97 and with my other problems I want it in tip-top shape.

Since remans are way too expensive for me at the moment I ordered new OEM brushes and will just have to see if it helps. If not I'll have a spare pair that fits both of my Toyotas while I scout for a cheaper reman

[Previologist]

My limited understanding is that the regulators almost never fail. Unfortunately the 93 and 97 regulators are not interchangeable.

[samstrader]

I rechecked my alternator purchase and I bought a remanufactured Denso alternator that was remanufactured by REMY. So I was not correct to say it was remanufactured by Denso. But it's still a Denso alternator. It is really working good so far.

[Previologist]

Upon closer examination I see that the slip rings where the brushes ride is badly worn, scant thousandths of an inch from wearing through. I also noticed that the Denso label says this is a remanufactured unit. If I am correct in what I think I'm seeing, they lathed off most of the copper when it was remanufactured in order to remove previous wear, because it looks paper thin even where the brushes haven't contacted it.

This area is called the "slip rings" but I don't see any such part on diagrams of our alternators so they seem to be part of the rotor and not replaceable. But the 93 has the same rotor and has much more copper left (its a full mm wider) so I may attempt a rotor transplant. I got the 93 rotor freed up now. I should probably have the store run a load test on it before declaring it a suitable donor.

I figure I'm in this rabbit hole this deep already, I might as well keep digging deeper. The potential symptoms of badly worn slip rings intrigue me.

Top: LOTS of copper left on the 93 "donor"
Bottom: hardly any copper on the 97. Its down to the width of the shaft it rides on.

[samstrader]

Upon closer examination I see that the slip rings where the brushes ride is badly worn, scant thousandths of an inch from wearing through. I also noticed that the Denso label says this is a remanufactured unit. If I am correct in what I think I'm seeing, they lathed off most of the copper when it was remanufactured in order to remove previous wear, because it looks paper thin even where the brushes haven't contacted it.

This area is called the "slip rings" but I don't see any such part on diagrams of our alternators so they seem to be part of the rotor and not replaceable. But the 93 has the same rotor and has much more copper left (its a full mm wider) so I may attempt a rotor transplant. I got the 93 rotor freed up now. I should probably have the store run a load test on it before declaring it a suitable donor.

I figure I'm in this rabbit hole this deep already, I might as well keep digging deeper. The potential symptoms of badly worn slip rings intrigue me.

Top: LOTS of copper left on the 93 "donor"
Bottom: hardly any copper on the 97. Its down to the width of the shaft it rides on.

I took the brushes off my original alternator that had 435000 miles on it but I don't remember how much copper was left on the runner. It was not scratched up too bad so I would have just put the new brushes on it without doing anything to the shaft. My brushes were worn completely down and the alternator stopped working when the brushes couldn't touch the shaft anymore. I sent it back as a core so I don't have it anymore and can't check it out for you.

[Previologist]

I took the brushes off my original alternator that had 435000 miles on it but I don't remember how much copper was left on the runner. It was not scratched up too bad so I would have just put the new brushes on it without doing anything to the shaft. My brushes were worn completely down and the alternator stopped working when the brushes couldn't touch the shaft anymore. I sent it back as a core so I don't have it anymore and can't check it out for you.

I had the 93 with its own brushes tested today. They were a little afraid it might blow up because of the PB Blaster smell haha, but it passed with FLYING COLORS, cranking out 14.5 volts. I will clean off any residual on the rotor with something, but I don't know what. Isopropyl?
KIMG1488.jpg

The transplant attempt will move forward. I think I will transplant the diode assembly too, since it is obviously fine. I suppose I should source and price bearings before getting too excited, although my 97's bearings are fine I don't know if they will be fine once I get them off.