# Haldex wiring and questions



## Cedmonds (Apr 14, 2014)

I was investigating a Haldex 65535 internal control module memory error and this is what i've found. 











I repaired the wiring and checked the fuse, the fuse surprisingly wasn't blown but i'm still generating the error. Is it possible this wiring has fried the controller? I pre-emptively purchased another gen 1 haldex controller off the marketplace here but have no real idea if its going to be any good other than the sellers assurance, can I plug it into the harness and test it with the Vag com without bolting it up just to make sure it can even communicate? I think that is what is going on in this video https://www.youtube.com/watch?v=VzAquasaHFc. I can hear the pump kick on with the vag com test so I figure the wiring has been repaired properly.


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## Mt. (Nov 12, 2015)

*Operational*

Does the Haldex still operate correctly? I'm new to TT and AWD, AND Haldex so I will follow this thread. Thanks!


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## bwdz (Jan 21, 2015)

Since you have a vagcom you can run a test on the modules. You can turn the pre charge pump on and off and engage and disengage the clutches. I don't recall where it is but somewhere in there it will run the test for you. I could actually hear the pump and the clutches when the test cycled them. I did this in a parking lot and if you cut your wheel all the way to either side and drive slowly (at idle or so) while it runs the test you will feel the binding in the drivetrain when it engages the clutches (like the 4wd bucking) and then it will roll freely when it releases.


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## Cedmonds (Apr 14, 2014)

Thanks! I checked the precharge pump and its loud and clear, I didn't think to check the clutches but i'll do that but I've already begun ripping out the old controller and boy is that tucked up in there, I got around it with an air compressor to dry to blow all the rust and debris away from the area before i even attempt to get those hex screws out. I'm actually probably going to pull the pre charge pump and clean it out somewhat, I saw the tech where the guy did that and it makes enough good sense to me. I also got the new filter and fluid and a power track insert so might as well throw it all together.


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## asiwa (Dec 18, 2014)

Hey man! Glad to see you're venturing into the Haldex dimension...godspeed to you 

It's possible that nasty wiring caused the controller to fail prematurely, but these controllers are known to fail for a number of reasons, the foremost being simple wear and tear from being located underneath the car in such a harsh environment. Bad wiring, fluid leaks, vibration and various other issues are not unheard of unfortunately. The internal memory error is also unfortunately something that cannot be repaired  Sorry about that! The airbag modules in our cars are notorious for the same problem/code. Keep your eyes peeled!

Anyway, you actually can test the controller before you go bolting it back in there. Rest the module on something or simply on the floor and hook up the wiring harness, and go ahead and run the VCDS Haldex test. When you get to the "AWD Engaged" stage you will hear the controller make an audible high-pitched whine. This is the noise that the stepper motor inside the controller makes when it is engaged. You'll have to get your ear right up on the controller to hear it, but that will be the definitive sign. My old dud controller didn't make such a sound compared to my replacement, so that was the determining factor for me. Oh, and if you can get someone to run the test for you, get the controller in hand and have that person run through the screens - you'll actually feel the controller buzz/vibrate in your hand a small amount when the motor engages the pin.

Other than that the only obvious way to tell will be to install it - sorry for that inconvenience! I know how much of a pain it is  But good luck to you! Once you've worked on/troubleshot the Haldex you're a true TT owner


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## Cedmonds (Apr 14, 2014)

asiwa said:


> Hey man! Glad to see you're venturing into the Haldex dimension...godspeed to you
> 
> It's possible that nasty wiring caused the controller to fail prematurely, but these controllers are known to fail for a number of reasons, the foremost being simple wear and tear from being located underneath the car in such a harsh environment. Bad wiring, fluid leaks, vibration and various other issues are not unheard of unfortunately. The internal memory error is also unfortunately something that cannot be repaired  Sorry about that! The airbag modules in our cars are notorious for the same problem/code. Keep your eyes peeled!
> 
> ...



That was exactly the information i was fishing for, Thanks! and believe me, this is no inconvenience. I'm so used to paying my automotive penance its become Stockholm syndrome. Its almost as if suffering is a normal part of car ownership umpkin:


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## Zelgin (Dec 7, 2013)

My Haldex controller comes up with the same memory error. But, the pump still runs and clutches engage, both in VCDS test mode and real world conditions. My driveway is an uphill dirt road, so, if it wasn't working, I'd know it. I picked up another controller, but haven't decided if there is a real good reason to install it, until the old one no longer gives me rear wheel engagement. In my case, just because the error exists, doesn't mean it's not doing its job. I'd welcome any opinions on why I should change it out, if it seems to be working.


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## asiwa (Dec 18, 2014)

Zelgin said:


> My Haldex controller comes up with the same memory error. But, the pump still runs and clutches engage, both in VCDS test mode and real world conditions. My driveway is an uphill dirt road, so, if it wasn't working, I'd know it. I picked up another controller, but haven't decided if there is a real good reason to install it, until the old one no longer gives me rear wheel engagement. In my case, just because the error exists, doesn't mean it's not doing its job. I'd welcome any opinions on why I should change it out, if it seems to be working.


Interesting! I absolutely believe you; It's just that all the occurrences of that code I have encountered have coincidentally been bad controllers, and thus it was an assumption I had made. That's great that yours is still kicking though (knock on wood ) and obviously I wouldn't worry about it until you start losing rear wheel grip. I'm sure you'd know it if you felt it :laugh:


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