XC90 2.5T 140a alternator regulator brush wear/replacement

Post by **ggleavitt** » 31 Aug 2018, 10:42

Apologies for the cross-post but I changed out my alternator regulator a couple years back (proactive maintenance) and thought to post since this is a job I suspect will come up more frequently in older 5 and 6 cylinder P2 cars.

Super easy to replace if you're already in the area doing a belt, and may extend the life of your alternator a few years for less than $40. I did mine with the alternator mounted on the car, reasonable amount of space.

https://forums.swedespeed.com/showthrea ... eplacement

edit 8/31/18- did in place

Post by **oragex** » 01 Sep 2018, 04:27

These replacement regulators are sometimes more fragile than the original ones (yes they are made by Bosch but it seems they don't last as long). Good idea not to throw away the original regulator if it was still in working condition, put it aside as spare just in case.

Post by **ggleavitt** » 01 Sep 2018, 11:37

Good to know, thanks for bringing it up.

Would this suggest a replacement (rebuilt) alternator might have the same shorter life ?

The regulator is pretty common across the alternator line and OE is $200+, if there's a higher quality Bosch part out there that costs less but gives the same result, might be good to note as a preferred replacement PN for longevity sake.

Post by **mrbrian200** » 01 Sep 2018, 13:02

I had my alternator rebuilt at 85k miles as preventative. They showed me the original brushes that came out of it, 75% worn compared to a new set. 100k miles per set of brushes is probably about what to expect from them. The regulator is likely engineered to last around the same amount of time since most people don't bother replacing brushes only but instead replace the entire alternator new/rebuilt where both items would both be fresh. There's no point to designing the regulator to last forever when 99.9% are just going to be thrown away as 'standard procedure' during a rebuild service anyway.

Post by **oragex** » 01 Sep 2018, 13:55

The rebuilt alternator bodies can be a hit or miss (ex if it has a cheap chinese clutch pulley that's not a good thing), someone mentioned that even Bosch had two qualities on rebuilds...I think on the cheaper one of them the number ends with an "X"

I've pulled brushes (regulators) from 130K+ miles cars, there were still some 25% left on the brushes but I guess this depends on how is the car being driven (highway only means lower rpm, city driving may wear these more)

As for the original alternator, it does fail at the clutch pulley again after quite a few miles - hard to predict but I would guess 150k miles would be a good bet. So even when replacing the regulator, one should expect the clutch pulley to also wear at some point. This can easily be checked by hand with the belt off (shown on youtube)

I for one I prefer just pulling a used unit from the scrapyard and keeping it as spare. $50 and when mine goes bad I just swap the spare one.