# Haldex Controller teardown and fix



## B1-16V (Aug 5, 2002)

I've been debating making this thread for a couple weeks, due to lack of traffic here, but thought I might as well, since it might benefit some lurkers.

Long story short, my car was binding pretty bad after replacing the cargo pump. It never seemed to stop. It would completely stop on a slope with the wheels turned, while at idle.
I believe I have fixed the issue. The controller pin seemed to be stuck in the up position. 

As always, YMMV.

So I decided to tear apart my controller. I thought what have I got to lose. The bind was so bad, I knew it was going to ruin something. May very well have taken some life out of driveshaft couplers, CV joints, wheel bearings, who knows.

I didn't really know what to expect, but I sure didn't expect to find oil filled up inside the electronics or in the stepper motor. Completely filled.
After studying it for a bit, it was clear that a couple of seals were just not doing their job, and let the oil past.
Good news was that the stepper motor was very clean, looked new. Just oily.

As soon as I took the stepper motor loose, I heard a slight pop, and realized the plunger pin (metering pin) was in the UP position, while it was out of the car. Clearly this was causing the constant on of the AWD.

So I cleaned it up, and got out my collection of assorted O-rings. There is an O-ring about 3/4 inch diameter that goes on the face of the stepper motor, and it seemed way too skinny. Made no resistance when pushing the motor in place. Replaced that.
That larger one is why there was oil in the housing. 

The other issue is on the stepper motor shaft. It is a tiny little seal, in the shape of a cup. I altered that seal, (removed the metal "spring" part).
The seal just isn't the best solution apparently. There is very little travel to the shaft, it only does a few rotations (don't quote me, I didn't count) for it to raise the plunger up and down. It's not in constant high speed long duration rotation.

So, that's about it. I just changed the O-rings, added 2 where there was none, re-sealed the housing, and put it back in.
The car is no longer binding. 

I was concerned that maybe the AWD was not going to work at all after doing all this. Well, it certainly is. I can now turn full lock on a slope, and the car just glides around. And in the rain, well, it behaves like it always has - almost undetectable slip, and just takes off.
I couldn't be happier.

The O-ring pics are probably a bit confusing, and not super precise. But I know that anyone willing to go this far and take theirs apart will be able to figure it out. You'll have to take it apart first, THEN go to the store. 

Bottom pic show the tool I sort of made up to get the controller out. Was a long T handle Allen, and I inserted into a stubby Allen socket.
Going in from that area allowed more torque to remove the original bolts easier.


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## carsluTT (Dec 31, 2004)

THANKS for making a thread! as slow as it is on vortex these days it is still the go-to place for info! :beer:


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## asiwa (Dec 18, 2014)

Wonderful work. This board may be quiet but this info will definitely benefit quite a few people who still run their cars. I've been through two controllers already but still have them laying around - maybe I'll have to tear them down and check it out. 

Sent from my Pixel 2 XL using Tapatalk


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## B1-16V (Aug 5, 2002)

Part of the reason I was hesitant to post this is because I am wondering 2 things - 

1) How long will this last, will the high pressure oil get past my seals eventually, and how soon....

2) Why exactly was the plunger in the up position anyway? I'd think, even with the oil in there, that the spring pressure on the piston would be enough to push it back down. That piston area always has oil around it.

So, I'm not 100% confident that I really "solved" the issue, I just know that my piston was 100% in the up (full AWD) mode, even when unplugged, out of the car.

I did learn a TON about the system though, and if it acts up again, I might come up with some other ideas how to tackle it.


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## velocitychris (Jul 16, 2011)

I'm always so happy and grateful to find DIY posts. They have helped me so many times. Thanks for the work (and I am hoping to not have to need to reference this, but happier knowing that it is here)


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## lite1979 (Sep 9, 2005)

Thanks for posting this! I'll be doing similar surgery once I get my truck back on the road and don't have to daily my TT.


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## Ausparky (Feb 5, 2021)

Hi great post this is exactly my problem thanks . Just a quick question how did you get the cog off the stepper motor to get to the seal ?


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## B1-16V (Aug 5, 2002)

Ausparky said:


> Hi great post this is exactly my problem thanks . Just a quick question how did you get the cog off the stepper motor to get to the seal ?


Well, after a year and a half, I'm afraid I can not remember the details of getting the cog off. Sorry.


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## Ausparky (Feb 5, 2021)

B1-16V said:


> Well, after a year and a half, I'm afraid I can not remember the details of getting the cog off. Sorry.


Thanks for your reply worth an ask anyway .


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## B1-16V (Aug 5, 2002)

(what happened to my pictures?!? argh.)
I'm sad to say, the car is binding again. I guess the O-ring fixes I did were not permanent.
So, with that said, the oil inside the controller area seems to not be a problem, since the rear certainly engages still. The issue is that plunger just doesn't want to go down.
I may revisit this project eventually and come up with something else.
Four ideas I've had floating around in my head -
1, redoing the seals, with something better. Obviously would mean a longer tear down, to actually do some machining and redesign of the seals.
2, adding some sort of spring to push the plunger down easier. Encouraging it to drop.
3, modifying the plunger with a slot to relieve the pressure. I suspect it's making some sort of vacuum not letting it drop. (I'm not really super confident on this one)
4, Just installing a switch that disables fuse 31 on demand. Might not be instant, not sure, but if you know you're going to be in a parking lot, at low speeds, you could disable the fuse, and the car would behave.
I'm really leaning towards this, because clearly the rear end is engaging very well, and this switch would just simply turn it off. If you forget to turn it on, you basically just have what all the non-quattro cars have. No big deal really. But the traction triangle symbol would be lit, so, not likely to forget. This essentially turns you into a 4x4 truck style AWD.

I think I will try a temporary option 4. Just throwing a switch in their, and have the wires dangling out of the side of the fuse box. Just to see if it's something I can live with. Eventually, I'll probably move a switch to the Air bag light location just behind the shifter.


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## mdjenkins (Feb 16, 2010)

B1-16V said:


> (what happened to my pictures?!? argh.)


Your picture's URLs are still there. Facebook is denying access to them (which is just like Facebook). I'm getting 403 (unauthorized) with the message "Bad URL timestamp" when trying to browse directly to the pictures.


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