LD28 alternator brushes

[goglio704]

I opened up an LD28 alternator recently to check the brushes and found one worn to the discard line and the other with 8 or 9 mm of material remaining. I'm thinking somebody must have replaced just one brush at some point? Maybe one of the slip rings has a rough spot that eats brushes? Seems to me that a rough spot would disappear over time. Weird - to me at least.

[Carimbo]

I have a spare LD28 Maxima alternator I pulled from a JY. Brushes on it are unequal length like you report, goglio704, yet nowhere near wear limit (6mm min.?) The short one is 10mm.

Recently inspected the brushes in my daily driver-- both equal length, approx. 15mm. This alternator looks to be in better overall condition; cleaner and less corrosion. Yet in the wintertime running w/ headlights on, heater blower, and windshield wipers it struggles to provide 12.9V at speed. The headlights (halogen sealed-beams) seem dim always but that might just be me comparing it to other cars on the road, majority are newer cars with much brighter lighting systems.

Out of curiosity: Does anybody know the length of new replacement brushes?

[asavage]

Yet in the wintertime running w/ headlights on, heater blower, and windshield wipers it struggles to provide 12.9V at speed.

That's definitely insufficient. You may have a failing diode. See the pics I took of physical damage to some diodes I had last year. Or get a free load check at one of those specialty battery/alternator stores.

Bad brushes can give low output, but only toward the very end. Unevenly worn slip rings too.

[Carimbo]

Seems like the voltage drops over time, ex: after 1 hour runtime. Does that make any sense? Could it be heat related? Charge voltage upon initial startup appears satisfactory-- 13.4-13.6V.

[asavage]

Yup, bad diodes junctions. You saw the pics I posted in the other thread? The anode comes loose from the substrate. That alternator actually would generate about 10a output max.

I expect that when it gets warm it performs worse.

Those are soldered in, BTW.

[asavage]

Followup: any change, Caxambu?

[Carimbo]

Took the car to a FLAPS to test the alternator output but their tester was broken, planning to take it to another soon. So, alternator still the same; nothing new to report.