Alternator minimum brush length ?

Mike98 · Post by **Mike98** » 03 Apr 2025, 16:21

My 2006 V70 NA has 116,000 miles. The intake manifold is off because I am replacing the PCV breather box and hoses. This is a good opportunity to check the alternator because it would be easy to remove/replace if necessary. The alternator pulley and bearings seem fine. I removed the alternator back cover and voltage regulator to check the brushes.

One brush extends 7.5 mm beyond the holder and the other brush extends about 9.5mm. See the 2 pictures below.

What is the minimum brush length for reliable operation ? Any guess at the remaining mileage for my brushes ?

Thanks,

Mike

2006 V70 NA M56 116K

Vova585 · Post by **Vova585** » 03 Apr 2025, 18:09

They look like they should last at least another 10k or so. However for $32 I would put a new unit and forget about it for another 15 years.
I am not 100% sure but some alternators were coming with free spinning pooley. If you are there it is worth checking serpentine belt and if your pulley is still free rolling.

Post by **pgill** » 04 Apr 2025, 11:40

I replaced mine with about that much life left

https://www.freel2.com/forum/topic39641.html

I agree with the recommendation to replace.

Post by **volvolugnut** » 04 Apr 2025, 14:53

My manual says 5 mm is minimum length.
volvolugnut

Post by **jonesg** » 05 Apr 2025, 17:34

I have a new regulator in the garage, its dark now but I'll measure the brushes Sunday.

Post by **jonesg** » 06 Apr 2025, 20:17

the new bosch one I have is just over 1/2 inch.
Yours are longer than my new one.

this one is 5/8ths.