Haldex Clutch Part Numbers & Compatibility

Hello fellow enthusiasts!

Once again, the troublesome topic of Haldex...

"On my S3, manufactured in November 2001, the all-wheel drive occasionally malfunctions, meaning:"

- If it's cold (below 10 degrees Celsius) and the car has just been started, it can be quite problematic when driving through tight curves. You can feel that a wheel is locking up, and you'll see the ESP light flashing. However, the car does have all-wheel drive.

- When it's warm, everything seems to work perfectly. The rear axle is engaged, and even tight turns can be taken without any problems. There's no binding, creaking, or locking up, etc.


Previous diagnosis:

- The vehicle's wiring harness has been checked. The onboard voltage, brake light switch, and handbrake switch are all functioning correctly. There are also 12 volts present at the pump's connector. The pump has a resistance value of 2.4-2.5 ohms at its contacts, and it runs smoothly when I manually apply 12 volts.

What seems strange to me is the following: when I measure the contacts for the bus, I get -1 with the ohmmeter once, and then when I swap the two probes, I get -18 to -20 ohms. Does this mean the resistance is infinite?

- Control unit: I can access it with VCDS, and the error memory is empty. When I start the actuator diagnosis, the connection seems to be interrupted.

I have another Haldex unit here from a car without ESP. I connected it to the wiring harness and also connected my pump to the other Haldex unit. The pump runs when the ignition is on, and diagnostics are possible, including actuator diagnostics.

Based on this, I suspect my control unit (STG) is faulty. Now the question is whether I can simply replace it with a control unit from a car without ESP (S3, year 1999) – it seems to function at least in a basic test.

Does anyone know how the part numbers for Haldex components are related to each other? I really need a reliable answer.

My part number is 02D 525 554 AD.
The other Haldex unit has the part number 02D 525 554 D.

The ECUs are the same, the old one has "B" at the end, and mine has "C".

I don't have the logs available at the moment, but perhaps I can still help you.


Thank you very much and best regards.
Alex.

Hi Alex,

Quote:

But I find the following quite strange: when I measure the contacts for the bus, I get -1 with the ohmmeter once, and then when I swap the two probes, I get -18 to -20 ohms - does that mean infinite resistance?

What kind of bus are you referring to? Regarding cable resistance specifically, it ranges from near zero to infinity.

First, you should check if all the ABS sensors are providing roughly the same speed values (see the corresponding measurement block).

Best regards, Rainer.

Hello Rainer!

Quote:

What kind of bus are you referring to? Regarding a cable resistance, it applies that this value lies between near-zero and infinity.

I meant the communication line between the diagnostic interface and the Haldex control unit. Is that a CAN bus standard?
However, since it's a very negative or infinite value, it should fit... as far as I understand.

Quote:

First, you should check if all ABS sensors are providing approximately the same speed values (see the corresponding measurement block).

I did that, and the results are very similar. However, I still created a log file!


Thank you very much, and best regards.
Alex.

Quote:

I meant the communication line between the diagnostic interface and the Haldex control unit (STG). Is that a CAN bus standard? However, since it is far negative or infinitely negative, it should fit... as far as I understand?

I would need to check the wiring diagram, but I suspect it's the CAN-Bus. If the communication works with VCDS, then the connection is likely okay.

It would have been simple if the wheel speeds had glitched or differed.
Often, the following problems can also be present: debris or rust on the ABS sensors or rings, loose wheel bearings, or damaged ABS rings.
Have you checked the tire pressure? In my car, I only noticed that one of the tires was almost flat when the ESP started to activate while cornering. }

Best regards, Rainer.