I have spent the last 2 weeks reading over pages and pages of forums and articles about Haldex issues on the TT and still cant figure my g/f tt out(ready to sell the thing!). Here it goes.... I noticed 2 weeks ago in a bad snow storm that I was getting tons of wheel spin, pulled into a parking lot and got out and had my g/f dump th clutch and saw ZERO rear wheel spin. I checked the brake lights and parking brake. Put the car up on my friends lift and changed the haldex oil and filter, then put it in 5th gear and let it idle. Still ZERO rear wheel spin. Got a Ebay Vag cable today and read the codes, came up with 00526 - Brake Light Switch 27-00 - Implausible Signal. Cleared the codes and still no rear wheel spin on the lift. I just ran out and did the Haldex test in Vag-Com where it turns the prepump on and engages the haldex clutch pack. Im not sure if its supposed to say it failed if there is a problem but it seemed to go through fine, I then had my g/f use the computer while I lay under the car and listen to the Haldex unit. I did not hear anything when the prepump was supposed to run but I did hear the solenoid engaging the clutch pack. So do you think it is the prepump or the controller being bad and not telling the prepump to turn on. I'm almost ready to order the Haldex Blue but I dont want to throw away $1000 if thats not the problem. Sorry for the long post, this is my first and thanks in advance.

 

In my case, it was the controller. See if you can borrow one to rerun the test(s) to see if it makes a difference. It did in my case. Not an easy task to swap that controller in and out though.


IIRC, there is a series of trials performed on a lift where the handbrake is pulled with the clutch engaged or disengaged with different results. (Engine stall or keep running, etc.) Sorry don't remember exactly.


Good luck.

 

copied from the FAQ


- AWD test on car lift. (all wheels free to turn.)

Aim: Check the function and the control of the coupling.

1. Pull the handbrake.
Disengage the clutch.
Start the engine.
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch.

* Engine is supposed to stop when the clutch is engaged. (HLSC controlled as in handbrake start.) If engine do not stop, disengage the hand brake immediately. Otherwise there is a risk of seriously damage on the HLSC.

2. Disengage the handbrake.
Disengage the clutch and start the engine
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch. At least one front wheel and one rear wheel is supposed to turn.
Pull the handbrake for 2 seconds.

* Front wheel is supposed to turn while the rear wheels are supposed to stop when the brake is pulled. Engine is supposed to run all the time. (HLSC controlled as in handbrake turn.) Don't exceed the 2 seconds or repeat the test for more than 5 times during a 5-minute period. Otherwise there is a risk of seriously damage on the HLSC.<ul><li><a href="https://forums.audiworld.com/tt/msgs/1452481.phtml">Haldex Test</a></li></ul>

 

do your brake lights work? if not, 15 dollar part at VW or audi, your car will be FWD till then.

 

I was just too lazy to look it up

 

Brake lights works fine and code still hasnt come back

 

it could be an intermittent brake light switch, or perhaps a faulty connection along the brake light switch line. Also keep in mind when your car activates AWD, and you get some opposite wheelspin the front wheel you see spinning and the back wheel will be stationary. Open differentials..

 

I still am not getting the prepump to turn on when I do the Vag-Com test. I also unplugged the 2 prong connector and got a 12 volt readout coming from the Controller. So Im almost positive the prepump is bad because it is getting voltage but isnt turning on. Anyone know the cost, part number, and where I can get a prepump???