# Haldex gone - quattro no more - FIXED FOR 8€ !



## silkman (Jul 29, 2004)

Since two weeks ago, quattro wasn't working as the TT was spinning its front wheels in 3rd gear, which is something most unmapped TTs rarely do. Im gutted because I (again) face a €€€€€€€€ repair bill. [smiley=bigcry.gif]

Brief history:

The haldex and diff have been opened up 3 years ago and were rebuilt due to a grinding noise that has since been fixed. 4wd was always working in the past.

Pic from 2017 from haldex repair specialist









First step a week ago was the obvious filter and fluid change, the old haldex oil was quite murky and grey in colour. Not good. 









After new fluid+filter we run the car on the air to test it and all wheels were spinning and they did.
(not my car but you get the idea)




But as soon you would get it on the ground, no 4wd under normal load [smiley=bigcry.gif]. Note that until this point I would get the VCDS error, maybe once a week and no abs or engine errors in dash. No errors on other VCDS modules as well..









Today the replacement haldex pump arrived so off to the garage. Removed the old pump first and tested it with 12V and was good and strong, tested the new one too. Then we also removed the controller and opened that up to check for water ingress, nothing, it was clean as new inside. Fitted the new pump just in case -more wasted money :roll: and result same as before, it would work on the ramp but not on the road.

New pump (Borg Warner part - take note for reference)









No VCDS errors on AWD or brakes or engine since last oil and filter change a week ago.

I phoned up and discussed the problem with the shop that rebuilt it 3 years ago and he said there are many things that can go wrong inside, apart from the clutch pack which could be eaten up (that would explain the murky oil before) and offered to fix it again for a discounted price. However costs will rise up quickly eg. haldex discs 300eur, seals etc due to parts alone if I decide to go that route...

At this point i suspect the pump inside the control unit (which we *foolishly *didn't test with 12v while out of the car). This had an internal plug with 4 wires in it... [smiley=bigcry.gif] So there's another haldex pump which is inside the haldex controller

Haldex controller opened up, the square thing is the internal pump, pressure control motor V184 in repair literature









And behind a bracket on the other half of the controller is the board, examined it under magnification and looked fine









No VCDS errors today after refitting everything. And I'm running out of ideas... :?


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## davebowk (Aug 16, 2019)

Have you tried the pressure control valve I think it's the one that you can change to give a permanent 50/50 split.

It could be faulty limiting the pressure to the pack.
Sounds like it's trying to work so either low pressure to the disc pack or worn out discs.


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## silkman (Jul 29, 2004)

Can someone confirm, on VCDS *AWD *module when you run the output tests, can you hear any noise (eg a pump working)? In mine it completes the test successfully but no pump noise can be heard...

(google random pic - AWD, not engine module)










davebowk said:


> Have you tried the pressure control valve I think it's the one that you can change to give a permanent 50/50 split.
> 
> It could be faulty limiting the pressure to the pack.
> Sounds like it's trying to work so either low pressure to the disc pack or worn out discs.


Thanks for the reply. Not sure how that would work if one pump is busted (or clutch discs are fe$%ed)


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## davebowk (Aug 16, 2019)

silkman said:


> Can someone confirm, on VCDS *AWD *module when you run the output tests, can you hear any noise (eg a pump working)? In mine it completes the test successfully but no pump noise can be heard...
> 
> (google random pic - AWD, not engine module)
> 
> ...


I didn't realise you had found that a pump was knackered.

Over here you can get a full haldex unit off ebay for about £120 to £200, not sure how available they are over there.


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## desertstorm (Apr 25, 2017)

Hi, there isn't an internal pump in the haldex module, that is a valve that modulates the pressure to the clutch packs and engages or disenengages the haldex. When you are running the VCDS test the external 12V pump you have changed should run and you should hear a small whirring noise from the Haldex control unit when the valve is operating. This is fairly quiet though.
Have you checked the earth strap from the back of the rear axle assembly to the chassis. This rots and can cause issues.Mine fell apart when I went to touch it. The 12V pump needs to be running for the haldex to engage correctly.


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## silkman (Jul 29, 2004)

Thanks for the reply Karl. I thought one could hear something working when doing the VCDS output test. So I will try testing again the replaced pump as it makes a characteristic noise. If that doesn't work, probably the haldex controller should be replaced next.

A few weeks ago I touched the haldex earth strap and it disintegrated into dust, it was promptly replaced with a thick cable.


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## culver10 (Jun 26, 2019)

Yes, you can here the precharge pump running when you do the test.


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## silkman (Jul 29, 2004)

culver10 said:


> Yes, you can here the precharge pump running when you do the test.


Thanks for confirming as well.

I went to a quiet place and hooked up VCDS, laptop outside the car to test haldex again. The pump definitely can be heard when doing the output test (with engine off) so I'd rule out the controller for now. But you can't hear it from inside the cabin even with engine off. And still no VCDS errors...






So I guess its a haldex rebuild or finding a used unit... [smiley=bomb.gif]


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## GARAGE HERMIT (Mar 7, 2015)

if the haldex controller is u/s you usually get a grinding/klunking noise when reversing, mine did, 
bought a used one off ebay £80, luckily it work's fine,


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## silkman (Jul 29, 2004)

Fixed! Can you F believe this?

Friday I went to the usual garage after a call from my mechanic that he found a used haldex for replacement. We agreed to talk Monday as cost+fitting would be 500-600 eur [smiley=bigcry.gif]. New from Audi is 4000+

But something didn't feel right as last night I thought about all those intermittent brake switch errors. Looked on parts and the brake switch is 4pin, this means that it measures the same thing twice, like the green coolant valve. Its also a cheap part. Brake lights worked perfectly of course. Today I removed the old switch from the car (1j0945511b was the original), phoned a few shops and found an aftermarket switch for 8eur nearby. Crappiest aftermarket "fae" brand that I have never heard of but got it anyways because, you cant find better on a Saturday.

Old and new, preferable aftermarket is Hella part (also purple, 6DD008622731 Hella part number). OEM is made by Eaton









Got it and replaced it as its very easy to do. It included instructions to pull the lever completely out, press the brake pedal with your hand and fit it. Same exact instructions in Audi service manual. It makes a loud click when it goes in and the brake pedal returns to set it into place.

Then loaded up vcds and run a few scans. Strangest thing, on vcds awd module measuring blocks, the brake switch would show on and off correctly but the handbrake would show activated, and we all know haldex doesnt work with the handbrake on.









Next step check the handbrake switch before replacing that as well. It was a bit fiddly because you should remove the hand brake cover, the cover in front, remove the switch from the handbrake and remove its plug which took ages. Checked the switch with a multimeter (it worked), checked the plug (it wasnt shorted) and put it back in its place. Running vcds and handbrake activated worked correctly in awd. So removing it and putting it back somehow fixed it (usual situation)

Cover in front of handbrake









Guess what, took the car for a spin and it was quattro again 8)

Obviously all this time, brake lights worked correctly and also handbrake indication on the dashpod was correct if you would pull and release the handbrake. But somehow the second sensor on the brake switch was busted and that would send a "handbrake on" signal to haldex and it would deactivate. And I can only assume that the dirt in haldex oil was assembly lube from the previous rebuild :roll: 
How we missed the handbrake always activated previously I can only wonder 

As Hoggy says, "nothing is simple on the TT". So it was fixed for 8eur and 125eur wasted on the unneeded haldex pump...


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## Hoggy (May 8, 2002)

Hi, Very interesting [smiley=thumbsup.gif] 
Hoggy.


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## davebowk (Aug 16, 2019)

Yes, when you brake it disengages the haldex, i have intermittent brake switch errors but the brake lights work, (2 sets of contacts) it also is stopping me engaging cruise control sometimes. I have a new switch ready to fit.


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## silkman (Jul 29, 2004)

davebowk said:


> Yes, when you brake it disengages the haldex, i have intermittent brake switch errors but the brake lights work, (2 sets of contacts) it also is stopping me engaging cruise control sometimes. I have a new switch ready to fit.


Thats what made me replace it, the 2 sets of contacts. Although brake lights worked 100% didn't know what the second set was sending.


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## GARAGE HERMIT (Mar 7, 2015)

glad you fixed it, now you just need some snow to play in,


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## rlszer (Jun 9, 2014)

One of the reasons, I changed both the clutch and brake switches, quite a while back.


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## StuartDB (Feb 10, 2018)

That's great and the reason should be added to whatever FAQ we have for diagnosing quattro faults. 
Was the brake light switch highlighted in VCDS ?


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## corrado1.8t (Mar 22, 2012)

Was the traction control light on through all this?


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## davebowk (Aug 16, 2019)

StuartDB said:


> That's great and the reason should be added to whatever FAQ we have for diagnosing quattro faults.
> Was the brake light switch highlighted in VCDS ?


The brake switch will usually show as an intermittant fault with VCDS even if the brake lights are working.

It's just remembering to link this with other issues it can cause.
2 i know off are haldex and cruise control not working, i think it can also reduce the throttle/power if you keep your foot on the throttle and left foot brake for instance, but not sure if thats correct.


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## StuartDB (Feb 10, 2018)

When had a kia sedona, the EML appeared if you touch the brake pedal, then at the next service or if you ever have an issue they just changed it.

Also after I accidently put £10 of unleaded, and filled with diesel. A week later, it would regularly have issues, but never whe at garage. They used it for a few days and ended up having to change the ECU. It feels coincidental - I had a powerbox fitted, which essentially just upped the fuel pressure.


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## silkman (Jul 29, 2004)

StuartDB said:


> That's great and the reason should be added to whatever FAQ we have for diagnosing quattro faults.
> Was the brake light switch highlighted in VCDS ?


No 


corrado1.8t said:


> Was the traction control light on through all this?


and no, brake lights, handbrake indication on dashpod and esp were all normal.


davebowk said:


> StuartDB said:
> 
> 
> > That's great and the reason should be added to whatever FAQ we have for diagnosing quattro faults.
> ...


EDIT Its normal to see brake switch errors in vcds haldex module - read special notes below.
http://wiki.ross-tech.com/wiki/index.ph ... ble_Signal THIS IS LISTED FOR AUTO SO IT MAY OR MAY NOT APPLY TO YOU


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## StuartDB (Feb 10, 2018)

do you have an automatic - 1.8t?


```
VAG-COM-FAQ-2.7

2.7 Are there any Fault-Codes that can and should be ignored? 
 Yes. Most 1995 and earlier Bosch ECU's will show you a DTC 00513 - Engine Speed Sensor (G28) if you scan them when the engine is not running. This fault code goes away by itself once you start the engine. If this sensor were truly defective, the engine would not run at all! Please ignore this code. 
 In addition, many Automatic Transmission Control Modules will show a DTC 00526 or 17087 that indicates a faulty brake light switch. This can also be ignored and will not appear if you press the brakes once before checking for Fault Codes.
```


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## davebowk (Aug 16, 2019)

[/quote]Its normal to see brake switch errors in vcds haldex module - read special notes below.
http://wiki.ross-tech.com/wiki/index.ph ... ble_Signal[/quote]

Thats for an auto


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## silkman (Jul 29, 2004)

OK, I stand corrected! But yeah, I was getting some intermittent brake switch errors. And I think it came up again when I replaced it, but haldex definitely works.

Many aftermarket brand parts exist for this brake switch so it makes sense to replace it.


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