Haldex not working? No communication etc? Look inside

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badger5

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If you have Haldex issues...
check out these pictures of an S3 in here yesterday with only fwd

Usual Earth strap broken and very corroded generally around the fixing..
haldex-earthstrap-broken.jpg

Fixed by making up a new earth lead and replacing it.

Also... Check connectors for corroded pins..
haldex-plug-corrosion-1.jpg

haldex-plug-corrosion-2.jpg

haldex-plug-corrosion-3.jpg


Replacing both pin and socket in connector, with vag repair replacements, and the haldex pump started to work again and 4wd was once again working again.

cheers
bill
 
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Westy said:
Bill are you able to get a picture or give a description of where the earth strap is on the Haldex unit. Every time i've been under my car and looked for it I can never see it!
Click to expand...

this picture is take on passenger side viewed just fwd of the drive shaft.
bolt/strap are about at the 11 o'clock position and go up to a stud on the floorpan, which may also shear off when you look at it. It can get very corroded down there.
The plug connection is on the back of the diff, usually behind a small ally heatshield.. just in front of the rear silencer

haldex-earthstrap-broken.jpg



hope this helps
regards
bill
 
Thanks bill my cars running great now !
 
Does this fix work if there is a 'humming sound' from the unit when you turn it off? Or does the sound represent complete death?!
 
I found my earth strap was broken today when I was checking the rear xenon level switch. I did have intermittent output communication errors but interestingly enough no warning lights or other symptoms and the 4wd was definately working last week on a muddy field - I have repaired the strap anyway ...

Martin
 
Hey Paul

Im sure you have come across the other trhead about the 'dragging' wheels, do you know of or is Bill aware of anything that could be causing this, there are quite a few people that are having this issue, including me, so would be good if an 'expert' ;) could give a view or some advise on this or even a possible solution :)

Cheers
Nilz
 
Hi - I have the dragging wheels, and had to take fuse out to get the car back into two wheel drive mode. this has been really annoying me but every gargage I talk to seem to think they know what the problem is, but seem to want to charge through the roof to invesitgate. Have changed the Haldex controller, and complete a number of tests.

1. Driving along and pulling handbrake up - this dis-engages the haldex and drives, put hand brake back on haldex engages but wheels make a noise.
2. Pulling away in second gear - no haldex enagaged, front wheels slip and it engages and rear wheels start to lock (sound like they are)


Seems the haldex is confused and tries to engage at the wrong time.

Bill - I live in Orpington, kent, if you know anyone down this way you trust I can take my car to then please let me know. I had an ex Audi guy look at it and he noticed a grey tint to the Haldex oil, and stated the haldex was broke, before I spend any money on it I really want to know the fix, if its a new rear diff then great, if its not then I could be out of pocket £200 plus and still have the problem.
 
On my First S3 (7 years ago now.... ) i had a similar problem with the rear wheels dragging, it went to a number of different garages including a Stealers i replaced the controller, the diff still the same problem mine turned out to be the ABS ECU that was at fault, mine had no fault codes or error lights. a local VAG specialist fixed mine.
 
As a matter of interest, did you try removing the haldex fuse and did the problem go away ?. Handbrake trick ?

your the guy who replied to me with that information when I asked you 4 years ago ! When I was reading into this issue as much as possible.

The only thing I have to add is that with the knowledge I have built up surrounding this issue nearly all reports of this problem were solved by simply swapping out the complete rear end rather than messing around with individual components. YOU are the only one I have read that it was the ABS/ECU unit. But it's a possibility as it too communicates with the Haldex - i gather the abs unit also handles the ESP function (?)

The other thing, and call me skeptical but were ALL the parts replaced on your car with NEW or reconditioned parts before replacing the ABS unit ? And was the ABS unit new or reconditioned your old one ? I'm just thinking there may have been an issues somewhere with an earlier part which was replaced and they sold you the abs unit and fixed something minor (maybe!) just to justify it - after all that ABS unit is a fairly expensive part ! - I did say I was skeptical :)
 
Last edited:
Bill as Was said, I'd be happy to travel to Gloucester to get mine fixed! I've replaced the rear diff, the haldex pre charge pump, oil and filter change, front wheel speed senors and spent money on 'investigative' work.

Incidentally, the only error code I have is on my front driver's wheel speed senor, inspite of having it replaced. My local mechanics have looked into the electricals and they don't believe there is anything wrong with the loom. They did suggest either replacing the front wheel speed sensor again or that it could possibly be the abs ecu.

Currently I have fuse 31 out and therefore have the esp light on. If I brake hard, my abs light goes on too.

Any help would be appreciated!
 
note I have a 2005 2.0T quattro, so high jacking this forum a little. But like you Erf I have the fuse out so I can use my car. At the weekend I did the following:

Handbrake test - Haldex goes off, with it on it drags the wheels
Left foot braking test - this had not affect
Next test is to test power from ECU to ensure its getting to the back wheel, which I assume it is, but then I can isolate the issue to the rear.

The car did however pull away fine, and I had to spin the front wheels to engage the Haldex to work. Its like the Haldex is going on but then not releasing, therefore thinking the front wheels are spinning when they are not.
 
Dunno why but always assumed haldex in these cars didnt talk to VCDS hence the no communication during fault scans.

Anyway spotted this thread a few days ago and managed to get round to checking mine out yesterday. After a bit of faffing about looking for said earth starp i spotted it and it looked ok as was attached at both ends. But i thought i would give it a quick wiggle just to make sure and lo and behold it fell away from one side and was very old and brittle.

I went to undo the other end of the strap which connects to the shell of the car and rather than undo it just pulled straight off the car leaving a nice hole lol.

So i have done my best pikey magyver fix as i didnt have a replacement strap i found some of the really old mains cable that has 3 thick copper wires in it in my dads garage. So i stripped the ends and wrapped it round the bolt and bolted back into the haldex. cut the mains to the right length and made a new earthing point where the rear headlight adjuster bracket sits.

Gave my car a scan today and lo and behold VCDS talks to haldex and it did have a minor fault lodged in its brain so have no cleared that too and re-scanned with no faults :)

once again ASN and its members help again and let me fix a fault i never knew i had and would never of worked out on my own especially for the grand total of £0!!
 
this is definitely reviving a dead thread but may be of use to people. i've had haldex problems for approx 6 months, whenever creeping on the clutch and trying to turn (whilst parking up for example) or even with a small amount of acceleration it made a horrible noise, could never quite work out if it was a grinding noise or the wheels being dragged around. i had tuffty suggest to me in another thread to get the haldex unit serviced. Got the unit serviced last week (and met mr miller in the process)

IT WORKS! all grinding/dragging noises are gone, and i dont know if it is just me but it feels so much smoother when cornering at speed now.
 
Ive recently been told by local vag specialists that my 2001 s3 AMK does not have an earth strap for the haldex, can anyone confirm this as true?

I've also recently sorted the dragging wheels issue by changing the haldex oil and filter, all for 65 odd quid from eBay

Cheers
 
my 2001 a3 quattro doesn't have one either and never has done as the stud on the floor pan where it would attach is all covered in the underbody stuff.So shouldn't be anything to worry about, but could fit one I guess if you were bothered about it.
 
Ok cheers just wanted a second opinion before buying a new haldex unit, have a no comms fault and have read a lot about missing or broken earth connector being a common problem and quick fix.
New unit it is then

Cheers
 
peterjacks84 said:
Ive recently been told by local vag specialists that my 2001 s3 AMK does not have an earth strap for the haldex, can anyone confirm this as true?

I've also recently sorted the dragging wheels issue by changing the haldex oil and filter, all for 65 odd quid from eBay

Cheers
Click to expand...

My 2001 AMK had a strap that was broken... I replaced it with a short bit of battery ground cable I bought from halfrauds

<tuffty/>
 
My 2002 AMK had a earth strap that was broken and has been replace, but I still have the issue on mine.
 
Last car I saw with the dragging issue was down to a faulty controller... pull the haldex fuse and see if the dragging goes... if it does then chances are its a controller issue

<tuffty/>
 
My haldex has always been fine but I found the earth strap broken about 6 months ago and just changed it with a battery negative strap from Halfords. There had been no issue anyway with it broken on mine.
 
I have esp light on over 15mph, the dragging has been resolved by servicing the diff (haldex oil and filter) but light still on (no comms). I'm a little confused over why some have it and some don't. I've read quite a bit about faulty/missing earth link being a major cause of the no comms fault. I just wanted to eliminate all the cheap options before buying a new controller.
Thanks for your help chaps
 
Paul ive removed the fuse on mine and still have the same issue!!

Looks like it may be a replacement controller.
 
My 2001 AMK had the earth strap and was also snapped causing the dragging wheels issue.

Made an earth strap and still wasn't working correctly, looked at the connector.. when I pressed it together than haldex came on (tested with vagcom) soon as I let it go it wouldn't communicate.. Fixed it by forcing the connector together with cable ties :jester:
 
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From the back, but you can hear noise from the front too....well you can on mine if you are on full lock.
 
Since this is the Haldex thread that is referred to in the stickies I figure I may as well post here so it can help people in the future (if someone manages to answer my question).

My haldex is on constant 4wd (even with the fuse pulled and/or the handbrake on). This makes tight cornering (especially parking) a nightmare.

The haldex has recently been serviced and has plenty of oil.

Are there any steps I can do to try figure out what is causing this? I would prefer to give it my all before I pay someone to do it. Thanks
 
I've seen that thread. I'm really hoping it is something more simple than that. I was wondering if anyone had any tests I could to do see if it is the pump etc.

Thanks for the reply though
 
If you have pulled the fuse, then the pump won't be running and the diff can't lock. Check to make sure your pulling the right fuse out, do the abs and esp lights come on the dash when you take the fuse out? or another way to be certain it's mechanical rather than an electrical fault, disconnect the plug at the rear of the diff, this will disconnect the power going to the haldex controller and the pre charge pump.

DSCF0511_zpsb9323387.jpg
 
rupe said:
If you have pulled the fuse, then the pump won't be running and the diff can't lock. Check to make sure your pulling the right fuse out, do the abs and esp lights come on the dash when you take the fuse out? or another way to be certain it's mechanical rather than an electrical fault, disconnect the plug at the rear of the diff, this will disconnect the power going to the haldex controller and the pre charge pump.

DSCF0511_zpsb9323387.jpg
Click to expand...
Quite sure I pulled the correct fuse. I will disconnect the plug. Thanks for the tip. If I disconnect the plug and it's still 4wd I'm guessing signs aren't good?
 
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Hi all, I have a 2004 8p 3.2 v6 - mine is stuck in FWD - with an error 0448 Static fault on clutch pump. I'm just working through some of the basics - the control unit pcb looks fine although there is some corrosion on the box so water may have come in.

My question though - I cannot for the life of me find an earth strap - does this exist on an 8P? anyone have any pics?

Also, i've been advised to take a reading across the pump - expect about 5 to 15 ohms - basic question can anyone describe which points of the pump i need to read - not something i'm familiar with.
 
You'd get better results asking in the 8p section as your pump/ system is different to ours
 
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