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[Kevin Wood]

You won't find a voltage at the ABS sensor. It generates an AC voltage when the car is in motion but it won't have a supply to it.

What the guy with the Tech 2 should have done is watch the wheel sensor output while the car was moving to check the reported speeds from all 4 wheels. That will tell you if you've got a totally dead sensor or just a reluctor ring that's missing pulses. Either way, it's not a difficult fault to solve with the correct diagnostics.

[terry paget]

Thanks Webby the Bear for that splendid demonstration of the easy out. I know them as screw extractors. I have used them in the past, the tricky thing can be drilling the hole in the screw centrally and as big as possible. I have two boxes of them on my garage shelf, missing the smallest extractors that I have broken off. I have found that if the head breaks off the screw or the hexagon rounds it is because the thread is rusted solid. then the only solution is heat.

[terry paget]

Thank you dbug. I did not know that. I cannot see how I should have divined it. Perhaps the envelope symbol and the talk of PMs should have told me.

[terry paget]

Thanks Kevin. The guy with the Tech2 was a generous sales director of a local Vx dealership. I go along occasionally when I am in trouble and he takes pity on me plugs in his Tech2 and tells me what it reads. In this case it said right hand front sensor not present. It's still puzzling, because it is still there, and is not open circuit, about 700 ohms, same as all the others. More puzzling is that when I plugged spare sensors into the RHF socket the ABS light remained on. But maybe the car has to move before it accepts a new sensor and turns its light off. I am under the impression that the front reluctor rings have no way of misbehaving, unlike the rear rings which have.

The front right sensor is now the chief suspect. Pity its stuck in.

[Shackeng]

Thanks Kevin. The guy with the Tech2 was a generous sales director of a local Vx dealership. I go along occasionally when I am in trouble and he takes pity on me plugs in his Tech2 and tells me what it reads. In this case it said right hand front sensor not present. It's still puzzling, because it is still there, and is not open circuit, about 700 ohms, same as all the others. More puzzling is that when I plugged spare sensors into the RHF socket the ABS light remained on. But maybe the car has to move before it accepts a new sensor and turns its light off. I am under the impression that the front reluctor rings have no way of misbehaving, unlike the rear rings which have.

The front right sensor is now the chief suspect. Pity its stuck in.

I think that may be correct, as I had an ABS light on daughter's MG after having it on stands and turning rear wheels by hand, thus turning the diff, such that a discrepancy was monitored by the ABS, but it went off as soon as it was driven.

[terry paget]

Thanks Shackeng.

I now have the hub off the car. As advised last Friday by my best friend, Ray Hardcastle. aged 83 and now sadly dying of cancer, I put a hacksaw cut  across a diameter of the screw, hammered the hub body where the screw enters, and applied a screwdriver to the screw head - and it turned!

However, with the screw removed, the sensor is still stuck in the hole. I have applied WD40 and am giwing it half an hour to seep through.

Comments invited.

[05omegav6]

Plus gas is alot more effective 

Allow to soak in, remove the wheel bearing assembly (if not already done), then apply heat to the hub and you should be able to drift the sensor out

[sassanach]

wd40 could'nt soak into a sponge

[sassanach]

besides you will almost certainly destroy it trying to remove it.(unless you get real lucky)

[terry paget]

Thank you for your support Gentlemen. You were right, of course. I have now removed the sensor, it came out in three pieces. I am now cleaning out the hole to accept my spare sensor, though I am not sure why. My spare is one I tried to get off an explod car with an ABS fault. It came out damaged. I have glued it back together again, but am not too confident in it. As I seem to be betting the farm on this sensor being the problem, it has to be a good one. On e-bay there are lots of rear sensors, but no front sensors. We all know why. The only front sensors come complete with front hubs.That is the way I shall have to go.

[albitz]

I might have a spare front sensor if you end up needing one.Not sure,but if you get stuck give me a shout and I will have a search through my various boxes of bits.

[05omegav6]

Be in the shed somewhere I shouldn't wonder

[terry paget]

Thanks Albitz.
 I have now cleaned up the hub and the sensor hole to receive my spare sensor. The old sensor consists of a coil of many turns of fine wire with a permanent magnet down its centre and a pole protruding at either end. The reluctor ring end pole is located very close to the steps in the reluctor ring, and is as wide as the gap in the teeth of the ring. I must work out how that creates an alternating current of frequency matching the  wheel rpm.

[05omegav6]

O level Physics the passing of the ridges cause a disruption of the magnetic field which in turn causes a current to form in the coil. The abs module then translates this as required

That's after 6 pints of cider though

[terry paget]

Good thinking, ex taxi al.

This morning, bank holiday, at loose end, I decided to reassemble using my old repaired front sensor. On start up the ABS light came on, then went out. I backed car out of garage, parked, and went indoors to change to go for a long test. Turned car round, ABS light came on again. Bother.

Any opinions? What should I do next? I can now change the sensor easily, but can I get one cheaply? They are not listed in Trade Club book; I bet they are expensive. I can get a right front hub with sensor for £26 on e-bay and fit that. I could go back to Downside Motors and have a second Tech2 reading. Please advise.