Had my ABS sensor changed today...
 

...and changed back to the old one again.

The new one from Rimmer Bros says "Aftermarket" on it. I don't know if that is relevant since they must all be aftermarket by now.

Anyway, the braking was perfect before, but the ABS & Traction lights would stay on after the first start of the day. About a half hour later a restart would clear that up. This new sensor made the brakes do the scraping and grabbing thing.

The sensor was incredibly easy to change - bolt out (easy) and just pull/twist/pull and it was out. There was a bit of rust on the bearing/hub, but not so much. After the first fail, the rust was cleaned up with spray and a wire brush, but no improvement. So, old sensor back in and it is fine going forward, but a bit rough now when braking in reverse.

Is there some trick to these new sensors? I seem to recall someone filing the underside of the bolt flange to allow the sensor to sit a bit deeper.

Does any of this ring a bell with anyone or do I just send the sensor back to Rimmer Bros for a refund?

Thanks,
Glenn

The air gap is important Glen - have a good close look at the back of the threaded hole in the backplate and remove any surface rust, as this will prevent the ABS sensor from seating far enough in and accurately reading the magnetic reluctor ring.

Hi Mike,

Thanks, yes, I will have a look at the mounting surface and make sure it is clean. I have to find somewhere that I can do this myself to be sure it is as right as I can get it. Where I am now I can't safely jack up the car so later in the week I will find a solution. I will also confirm the length of the new one is the same as the old one.

The baffling part is that the car NEVER had the rough scraping grinding noise and feel in low speed braking before - only AFTER the new sensor was put in. And now, with the old sensor back in, it is just as smooth as before (going forward, anyway).

Cheers,
Glenn

That's what I had - put it down to both the bearing and ABS sensor being aftermarket items and cured it by filing 1.5mm off the back of the mounting bracket to reduce the air gap and allow the sensor to read the reluctor ring.

Awesome Mike. Great info. 1.5mm? That's a LOT, isn't it? Yeah, I'll give that a go - maybe work my way up to 1.5mm if necessary.

Cheers,
Glenn

Well, what to do...
 

I wrote Rimmer Bros to tell them what was happening and if they had some idea if to file the underside of the flange or not. Emily wrote back saying to fill out the Return Authorization form and the Warranty form. Then return the sensor to them and they would test it and, if faulty, send a replacement. Because that could take a week after they receive mine, she suggested I buy another one now and if the returned one was deemed faulty they would refund the price of the second new one.

Now, this all sounds pretty inconvenient and I won't see a replacement sensor for at least a week - more likely 10 days. AND if their sensor is faulty, I think I'd rather get one from Matt (DMGRS) as those are reputed to be good.

If I keep it and file it and it still won't work there certainly won't be a refund OR replacement.

What to do?

Cheers,
Glenn

I only filed mine down after testing it Glenn. The voltage changes from 0.7V to 1,7V as the reluctor segments pass the sensor. When tested in situ my sensor was missing the odd segment, but off the car with the sensor in one hand and the bearing in the other it read every segment when the two were held close together.

Have a good look at the backplate where the sensor mounts and clean off any rust that has lifted that will prevent the sensor from seating correctly.

I wouldn't file the sensor bracket down unless you are 100% sure that will cure the problem.

Thanks Mike. I will have another look at that back plate to make sure there isn't a rust scale there that's keeping the sensor a bit high. Odd, though, that the original sensor that I put back in is working fine (once it has had its half hour drive and restart - its morning coffee). Maybe the original one is still stronger than the aftermarket one.

Cheers,
Glenn

It is worth persevering with it, because i had one from Matt which did the same. In the end i managed to find one of the genuine OEM ones in a packet from 2004 which went straight in and worked first time. Worth a hunt around ebay for genuine.

What i found with the after market one, was that actually it wasn’t going all the way down the hole. It was pushing out against the backplate and the backplate wasnt rigid enough to keep it in the hole, so it would work fine for 5 miles or so, then work itself out and start failing again.

If the new sensor is missing reading the odd segment that is what you get - the system thinks the wheel has locked up and so activates ABS.