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Discussion Starter #1
My car seems to be eating front ABS sensors as I've now gone through five in 2 years. The last one has lasted 5 weeks. Obviously I'm sending it back for a replacement but this is getting ridiculous. You won't be surprised to know that I've been using cheapo 'aftermarket' sensors at around £20 each. Genuine RR ones are about 10x the price and a total rip-off. I'd like to go for some sort of middle ground in price but it's hard to know whether they are actually better sensors or just someone selling cheapo ones at an inflated price. Does anyone know of a source for better quality ones or indeed who the OEM is for these sensors? (I don't believe Wabco make their own sensors).

My car is a 2000 Thor with the later black box ABS / Traction control. My understanding is that the sensors are passive and therefore it can't be the ABS ECU supplying too much current / voltage and therefore 'cooking' the sensors. I may be imaging it but several of the failures seem to have occurred in heavy rain. Failure modes include open circuit across the signal wires and several cases of 'sensor X short to another sensor'. Although this is often a symptom of a failed ECU, I have tried an alternate ECU and it gave the same faults. Replacing the sensors (nos 4 & 5) cured it for 5 weeks.
 

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Discussion Starter #2
ABS Sensor shorted to another Sensor - Fix / Bodge

Having been plagued by these failures recently I did some experimenting and discovered that if you remove the offending sensor from the hub then the fault goes away (well it did on my car anyway). As a test I removed the copper sleeve, wound two layers of insulating tape around the sensor and tapped it into place. ABS now shows no faults and the three amigos extinguish. I haven't decided myself how sensible it is leave this as a permanent fix but at least it shuts up the warning beeps while I argue with the supplier over a replacement sensor (It lasted 5 weeks).

The faulty sensor has a fairly high resistance between one of the terminals and the case so the ABS ECU test must use an AC signal. I suspect it applies a pulse to one sensor and looks to see if there is any response on the other sensors. I'm having trouble understanding what this test achieves and why it is necessary but I guess Wabco have a good reason for it. I also wonder if the test is unusual and hence aftermarket sensor manufacturers don't allow for it in their designs and the pulse somehow damages the sensor? It's a theory that would explain why I'm eating sensors but pretty speculative on my part.

I also noticed that the 'copper' sleeve is actually steel with a thin layer of copper plate and is rusting fast. This is not a good idea as the rust will jam the sensor in the hub meaning you'll be very lucky to get it out without trashing it. It's possible that 'genuine' sleeves are solid copper (mine is an eBay pattern part) but if not then using grease (as supplied with some sensors) should help to stop the rust.
 

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Re: ABS Sensor shorted to another Sensor - Fix / Bodge

I have just checked in my garage and I have a new genuine L/R sleeve in a packet (FTC1374). I can confirm it is solid copper.
Not sure if a steel sleeve would interfere with the signal, as the sensor is located in a solid steel hub casting anyway. Though maybe it needs a non magnetic gap between the sensor and the housing. The insulating tape you used would have the same effect.
I used silicone grease on the sleeve when I replaced my sensors. I figured it would be more waterproof. They have not been out for 5 or 6 years so not been able to prove it.
 

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With after market stuff like that, I usually order from one of the big L/R suppliers such as Island 4x4 or Paddock Motors rather than Ebay.
I figure that if they had lots of customer returns on a part, they would do something about it and source them from another manufacturer.
There are some parts I would stick with OEM but it is a question of judgement.
 

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I find this very interesting, as I had a FB message from another owner, who has an earlier vehicle (1996/1997 from memory) which has been through 3 sensors now on the front/right in the last year or so, with them lasting about 2-3 months at a time.

I think he too has been using cheaper sensors as replacements - so maybe there was a bad batch of them at some point? or the manufacturing tolerances are out of whack.

I read in one of the ABS 'D' manuals I have that the sensor range should be between about 900 and 2k ohms for the ECU to see it as being valid when it checks them. I haven't been able to compare the earlier Wabco 'C' system, but as they use the same sensors, I guess this should be about the same.

I have also heard from others about the 'D' series ECU showing X sensor short to another sensor as being a symptom of a connection issue to the sensor. Generally ECU failure is ONLY if it's "LH Rear sensor short to another sensor" - any other corner, and it is then usually a case of it being sensor or connection issue.

Another owner who had this issue found in his case the problem was in the female connector for the ABS sensor to the vehicle loom. One of the metal sockets had 'relaxed' a bit, which gave an occasional bad connection to the sensor plug and threw an error. He tightened the socket a bit with a small screwdriver (bent something in a bit) to give a nice solid connection again when the sensor was plugged in.

Very interesting to note about having wrapped the sensor in tape it seems to have fixed it. I wonder if there is anything in the bushing that affects it.
 

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Discussion Starter #6
Not sure if a steel sleeve would interfere with the signal, as the sensor is located in a solid steel hub casting anyway. Though maybe it needs a non magnetic gap between the sensor and the housing. The insulating tape you used would have the same effect.

That's an interesting thought, I hadn't considered magnetic coupling. It sort of fits with the sensor working while the copper coating is intact and then failing when the rust breaches it. Can't provide a scientific explanation though. I have some spare sleeves - I'll see if replacing the sleeve has the same effect as the tape.

I don't think it can be the resistance test that is failing since the test 'passes' with the sensor not in the hub. It measures the same whether the sensor is in or out of the hub. I also think that you get a different error code if the resistance test fails - hence my speculation about some sort of pulse test.
 

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Discussion Starter #7
Copper sleeve is probably a red herring, I tried a new sleeve and still got an ABS error. Any part of the sensor case touching the hub gives an error. This includes the tip touching the toothed wheel. To get it to work I had to push it fully in (which gave an error) then drive a few yards (to push the sensor out) and the re-cycle the ignition to clear the fault. Not confident how long this will last so still trying to get a new sensor out of Rimmers. Note that the traction failure does not clear until the car has been driven and then the ignition re-cycled once the ABS fault has cleared.
 
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