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FLE39 10-07-2012 06:19 PM

alternator duct
Searched, only found 1 thread that really didn't go into detail. this is the first car I've owned that has a duct for the alternator. I'm sure it's there for cooling of the altnerator which is good. Does it have a filter or screen in the duct work somewhere? I mean, what is stopping leaves and dirt from entering it. Is that a maintenance items to take the duct apart and clean the leaves out? I'm goingto pull it apart make sure it's clean and clear for peace of mind.

aioros 10-07-2012 09:46 PM

There is no screen or filter in that duct. Everything that can fly in there will get in there.

Sent from my MB860 using Bimmer App

FLE39 10-08-2012 06:59 AM

HOw is that good? Is it being directed toward a cooling fin section or the internals. I can't imagine piping dirt and debris into the alternator is a good thing.

cn90 10-08-2012 07:02 AM

You have 2 options:

1. Install Vinyl Screen (Gutter guard from Home Depot for a few $).
I posted info on Step 12 here:

2. Get rid of the air duct (that goes from the body of the car ---> alternator itself).
My Honda and Volvo have no air ducts for alternator.

The air duct seems like a nice idea (if it works as intended). Unfortunately, leaves, debris fly in there, making it worse than w/o the air duct.

xraye39 10-08-2012 08:14 AM

I use the gutter card screening to block any leaf debris from getting in.

I put this in place years ago on both my E39s.

pleiades 10-08-2012 11:20 AM

Got Fiber?

BentValve 10-08-2012 11:24 AM

If you get a replica M bumper, it will block off the duct

FLE39 10-08-2012 05:04 PM

^ Fiber!! WOW! Did you put the duct back on or not? I just dont see the duct being that useful, but I also don't remember seeing any fins on the alternator. Like other alternators. I think most cars have the fan blade behind the alternator. so even at idle they have something.

pleiades 10-08-2012 05:39 PM

That wasn't -my- alternator but all these air-cooled units will have this problem to some degree. If you visit your local home improvement center and get a small roll of that flexible plastic netting (BLACK, about 6 in. wide) for rain gutters, you can cut a piece to size and strap it with small zipties into the front of the alt duct mouth but behind the grille piece on the bumper. It will eliminate most of this and no one will notice it's there. You can also pull the plastic tube connection off the plastic part on the rear of the alt. I've had my alt apart a couple times since doing the netting on the grille end and it was debris-free. First time I remove my alt, it had lots of maple "copters", pine needles, bee and hornet butts, butterfly wings, and even some Wrigley's chewing gum foil (probably from a jaded e39 owner....).

The alt has cooling blades on the front and rear edges of the spinning stator.

neilw 10-08-2012 07:53 PM

Just changed my regulator, and mine was filled with dragonflies.

FLE39 11-16-2012 08:05 PM

I vacuumed mine out with the shop vac. Full of fiber! I really would like to remove the whole d uct system. never owned a car with it before... would open upt he engine bay even more.

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