Haldex controller (pissy)!
01-31-2005, 08:37 PM
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Haldex controller (pissy)!
My ABS/ESP fault light came on last week, accompanied by an "All Wheel Drive, no communication" fault posted by the ABS controller. The failure re-occours immediately after a reset. I made my living for several years troubleshooting circuit faults in large mainframes, so I'm pretty well equipped to work with the TT's controllers and interfaces. The ABS, Haldex and ECU communicate via the Can Bus to perform the ABS and ESP functions. My Haldex controller has, in effect, gone mute. I've verified the integrity of the Can Bus and the voltage distribution to the connector at the Haldex controller. The Haldex controller's processor IS running, you can poll it with the VAG COM successfully (this uses the diagnostic interface, a different wire from the 2 wire Can Bus). I spent some more time on the Haldex today, pulling and disassembling the controller. Then I continuity checked the wiring from it's plug, through all of the intermediate connections, and on to the circuit board... all good. The board has mostly miniature and high density components, and it's submerged in a clear gelatinous goo. I've never seen anything quite like it. Without actual circuit diagrams, I can go no further. So, failing a flash of inspiration, I'll be ordering up the "race" piece tomorrow (the cheapest available replacement), and saying Adios to $800!
Man, this upsets me. The OEM controller lasted 85k miles. I think it's dumb beyond ALL reason to bolt a fragile, integrated circuit board to the side of the Haldex box, exposing it to heat, cold, vibration, etc. Failure seems inevitable. Haldex's literature say's the controller is environmental in it's design, and tolerant of the adverse conditions under your car. Well, how come they blow up??? The Haldex does place less drag on the engine, and fractionally improves fuel economy (relative to the Torsen). But I could of bought alot of gas with $800!!! Looking at the packaging, the circuit board should have been remote from the other functional items in the controller. With 12-18 inches of wire (times the 7 discreet wires) the board could be mounted inside the car, and thus protected from the elements. I'm sure it's useful life would be 3-5 times longer (or, the equivalent life of the car). I don't have a choice, so I'll be putting up the money. But I'll tell you, if this new one fails.... my days as a Haldex equipped car owner will be over...
PS: the controller is a PITA to remove, and even worse to put back. Proof once again (like the Haldex oil filter) that no thought was given to sevicability of the Haldex, in an Audi. We just took the Volvo design and stuffed it in there.
Man, this upsets me. The OEM controller lasted 85k miles. I think it's dumb beyond ALL reason to bolt a fragile, integrated circuit board to the side of the Haldex box, exposing it to heat, cold, vibration, etc. Failure seems inevitable. Haldex's literature say's the controller is environmental in it's design, and tolerant of the adverse conditions under your car. Well, how come they blow up??? The Haldex does place less drag on the engine, and fractionally improves fuel economy (relative to the Torsen). But I could of bought alot of gas with $800!!! Looking at the packaging, the circuit board should have been remote from the other functional items in the controller. With 12-18 inches of wire (times the 7 discreet wires) the board could be mounted inside the car, and thus protected from the elements. I'm sure it's useful life would be 3-5 times longer (or, the equivalent life of the car). I don't have a choice, so I'll be putting up the money. But I'll tell you, if this new one fails.... my days as a Haldex equipped car owner will be over...
PS: the controller is a PITA to remove, and even worse to put back. Proof once again (like the Haldex oil filter) that no thought was given to sevicability of the Haldex, in an Audi. We just took the Volvo design and stuffed it in there.
02-01-2005, 04:30 AM
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Re: Haldex controller (pissy)!
I feel your pain, and have some input for you.
1) A Haldex engineer has admitted that earlier controllers had some durability problems. The latest revision is supposed to have cured this.
2) My controller went out at about the same mileage as yours-on an 02. I was extremely irritated, especially as my dealer's tech tried to tell me the entire unit was gone ($4000!) and that the controller was not available separately-though their parts department would sell one!
3) My guess is that my unit, and likely yours, do not have an ECU failure, but rather a failure of the stepper motor or the valve that the motor controls. Mr Schwing has posted the official test procedure for the Haldex unit- I can supply it as well if you can't find it.
1) A Haldex engineer has admitted that earlier controllers had some durability problems. The latest revision is supposed to have cured this.
2) My controller went out at about the same mileage as yours-on an 02. I was extremely irritated, especially as my dealer's tech tried to tell me the entire unit was gone ($4000!) and that the controller was not available separately-though their parts department would sell one!
3) My guess is that my unit, and likely yours, do not have an ECU failure, but rather a failure of the stepper motor or the valve that the motor controls. Mr Schwing has posted the official test procedure for the Haldex unit- I can supply it as well if you can't find it.
02-01-2005, 04:33 AM
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More..
Failure of these procedutres as outlined indicates the controller,as opposed to the pump, is the problem.
My theory is that failure to change the fluid fouls the control valve. Many dealers-mine included- have not changed the fluid as specified. I now ask for the old filter at each change. FWIW, it took my (independent) tech 45 minutes to do the controller swap-remove pan and control arm when you do the job.
My theory is that failure to change the fluid fouls the control valve. Many dealers-mine included- have not changed the fluid as specified. I now ask for the old filter at each change. FWIW, it took my (independent) tech 45 minutes to do the controller swap-remove pan and control arm when you do the job.
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02-01-2005, 05:13 AM
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well, looking at how they placed it on the car...i figured that they designed the wrench after the
car was put together. I'm sure it was an "oops" moment when they figured out that they couldn't get at it when the first TT Haldex controller went bad.
02-01-2005, 10:09 AM
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Your tech removes control arm and pan?
I believe the upper control arm on the passenger side would be helpful. I'm not sure which pan is indicated, though. Could you explain? TIA