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[Doctor Gollum]

https://www.ebay.co.uk/itm/314827804947

https://www.ebay.co.uk/itm/295477250260

[LC0112G]

Perhaps you are over thinkng the whole thing.

Given that the system doesn't work correctly with those sensors and that the sensors don't fit correctly, the simple fact is that you need the correct sensors. And possibly bearing assemblies. (Omega A and Omega B hubs may seem to be similar, but that doesn't guarantee that they are the same and it would be all too easy for the parts suppliers to make the same assumption).

Anything else is a waste of time and effort unless you're retired and extremely bored.

Trying to position the wrong sensors in the correct position is akin to trying to make a rear door fit the front door aperture... You might make it latch, but it will never function correctly.

I've never looked at the electronics inside an ABS control unit. If I had to guess I'd say the differential input goes into a balanced op amp which converts the sine wave to a digital input. But that's a guess.

The issue with reluctance sensors is that their voltage output is very frequency dependent. Given that the system is supposed to work from 5MPH to 150MPH there will be a very large variation in the signal amplitude at these two extremes - small at low speeds, very large (as in hundreds of volts) at high speed. I'll try and set it up in a bench drill to measure/demonstrate tomorrow.

But the point is the system will be setup to work reliably from 5mph to 150mph with standard clearances. If you move the sensor too close, it may overload the system at higher speeds - I know this is an issue with the Lotus Carlton ignition sensor, which is also a variable reluctance sensor. If the gap is too small, the ignition module misfires at high RPM due to being overloaded.  The cure is to put in shims to space the sensor away from the timing wheel - there is a field service note in the dealer manual to do with this. It's unlikely to cause damage inside the control unit, but it can cause mis-triggers. The LC timing sensor spacing is specced at 1.5mm gap. The ABS sensors are similar, and 0.2-0.3mm clearance doesn't sound right to me.

[Doctor Gollum]

Incidentally, the Febi hub linked to above does at least look like the original part as displayed in your side by side picture.

And to Malcolm's last, that's a moot point given that the sensors clearly don't work or fit correctly.

The depth at which they're set is arguably as important as the orientation of the sensor head.

Actual live data from the ABS ECU would confirm the signal difference compared to the rears and highlight the specific fault codes. But that would only confirm what we know from the first post...

The new sensors are faulty. Whether that's by design or accident doesn't really matter, the net result is the same.

[dave the builder]

Buying second hand ,genuine knuckles with genuine ABS sensors would be a way back to working ABS
not cheap though as you'd have to fit them, then get an alignment 

what happened to the original sensors 

I purchased low mile Omega B2 hubs/sensors  as spares when i had omega As (Vauxhall Carltons) years ago 

[bkorven]

Buying second hand ,genuine knuckles with genuine ABS sensors would be a way back to working ABS
not cheap though as you'd have to fit them, then get an alignment 

what happened to the original sensors 

I purchased low mile Omega B2 hubs/sensors  as spares when i had omega As (Vauxhall Carltons) years ago 

Yep! New sensors will be ordered. But I think I use the old knuckles, and use some material inbetween to increase the distance if needed.

I don't mind the fitting, as I do all the work on my car myself in my garage. Since I've replaced suspension I'll need an alignment regardless. So that's OK!

The original sensors broke as I tried removing them, while replacing suspension parts. The Haynes book stated to do so, but it would not have been necessary. All of the problems I have with the ABS is just an unlucky side effect from wanting to replace suspension parts.

[bkorven]

Perhaps you are over thinkng the whole thing.

Given that the system doesn't work correctly with those sensors and that the sensors don't fit correctly, the simple fact is that you need the correct sensors. And possibly bearing assemblies. (Omega A and Omega B hubs may seem to be similar, but that doesn't guarantee that they are the same and it would be all too easy for the parts suppliers to make the same assumption).

Anything else is a waste of time and effort unless you're retired and extremely bored.

Trying to position the wrong sensors in the correct position is akin to trying to make a rear door fit the front door aperture... You might make it latch, but it will never function correctly.

I've never looked at the electronics inside an ABS control unit. If I had to guess I'd say the differential input goes into a balanced op amp which converts the sine wave to a digital input. But that's a guess.

The issue with reluctance sensors is that their voltage output is very frequency dependent. Given that the system is supposed to work from 5MPH to 150MPH there will be a very large variation in the signal amplitude at these two extremes - small at low speeds, very large (as in hundreds of volts) at high speed. I'll try and set it up in a bench drill to measure/demonstrate tomorrow.

But the point is the system will be setup to work reliably from 5mph to 150mph with standard clearances. If you move the sensor too close, it may overload the system at higher speeds - I know this is an issue with the Lotus Carlton ignition sensor, which is also a variable reluctance sensor. If the gap is too small, the ignition module misfires at high RPM due to being overloaded.  The cure is to put in shims to space the sensor away from the timing wheel - there is a field service note in the dealer manual to do with this. It's unlikely to cause damage inside the control unit, but it can cause mis-triggers. The LC timing sensor spacing is specced at 1.5mm gap. The ABS sensors are similar, and 0.2-0.3mm clearance doesn't sound right to me.

Thanks, that is very useful information, and good to keep in mind since with new properly working sensors I'll probably have to increase the distance again. I have a 1mm thick rubber cloth that should result in a distance of 1.2-1.3 mm, which seems to be within reasonable span.

[bkorven]

EPC says that Omega A, Senator B & Omega B/B2 all use the same front hub assembly, GM# 90486467 / Opel KAT# 16-03-194. Not carried forward onto newer GM models.

And you're right, it's very likely that there is only one source supplying the hub assemblies and they are rebranded with whatever the buyer requests. It's also very likely that actual production ceased years ago and that anything available of whatever brand is actually old stock, dumped on the market to the highest bidder or bought up by old stock specialists. There are simply not enough Omegas or Cateras left to make it worthwhile for anyone to tool-up and manufacture any new parts.

The Ridex parts you ordered and the ESEN-SKV parts you received should be equivalent to each other and the factory fit and should work.

How did you clean out the bores for the sensors?

The bores for the sensors were sanded using a rotary multi tool.

[Doctor Gollum]

EPC says that Omega A, Senator B & Omega B/B2 all use the same front hub assembly, GM# 90486467 / Opel KAT# 16-03-194. Not carried forward onto newer GM models.

And you're right, it's very likely that there is only one source supplying the hub assemblies and they are rebranded with whatever the buyer requests. It's also very likely that actual production ceased years ago and that anything available of whatever brand is actually old stock, dumped on the market to the highest bidder or bought up by old stock specialists. There are simply not enough Omegas or Cateras left to make it worthwhile for anyone to tool-up and manufacture any new parts.

The Ridex parts you ordered and the ESEN-SKV parts you received should be equivalent to each other and the factory fit and should work.

How did you clean out the bores for the sensors?

The bores for the sensors were sanded using a rotary multi tool.

In which case Dave's suggestion will be the most cost effective solution.

Although I strongly suspect that you're going to try and fudge your current set up and at best, it won't work correctly and at worst could kill someone.

[dave the builder]

If you haven't wasted money for an alignment yet , 
you have a great opportunity to save yourself lots of time and the cost of a second or third alignment (you'll need at least one )
put the original suspension back on, get some used/working knuckles with the genuine factory sensors fitted  .get an alignment
bin the coil over tat you fitted 
Omega/ Carerra is NOT a race car,  drift machine , low-rider
original suspension works well for a comfortable family car ,which the Omega is 

[bkorven]

If you haven't wasted money for an alignment yet , 
you have a great opportunity to save yourself lots of time and the cost of a second or third alignment (you'll need at least one )
put the original suspension back on, get some used/working knuckles with the genuine factory sensors fitted  .get an alignment
bin the coil over tat you fitted 
Omega/ Carerra is NOT a race car,  drift machine , low-rider
original suspension works well for a comfortable family car ,which the Omega is 

I'm lucky enough to have a friend who has access to a wheel alignment machine, so I can do it for free, and set it up however I want 

I've found original used knuckles for sale, but I'm thinking about whether they really need replacing or not. I might end up buying them, too.

I deeply regret buying the coilover-kit. I'm not trying to make it a racing car, or anything extreme. I just needed to replace some suspension part since it failed the equivalent to MOT here, and the whole thing derailed. My suspension was very worn on the whole, so I took the decision to replace it all. And while doing so, I loved the idea of having adjustable ride height. I just wanted the car to sit slightly lower, for the looks, and since I like a slightly stiffer ride. I learnt afterwards that the camber is not even adjustable in the rear, and I'm now contemplating whether I can modify the rear suspension somehow, in order to adjust camber. It's gone too far, lol.

I really do not want to throw away the new coilover-kit. Also, everything is installed and ready to be aligned. It took very long.

I do not have the ride height set very low, and if I find the camber angle to be very far off I will either raise the height or try to find a way to adjust the camber.

I'm deep in the shit! If I had the opportunity to redo my original decision, I would choose to replace everything with new OEM parts. I don't want that now, because of all the time and money spent. Besides, it looks great being slightly lower than stock.

[dave the builder]

I've found original used knuckles for sale, but I'm thinking about whether they really need replacing or not. I might end up buying them, too.

original used knuckles may well come with original ,working sensors (which is why i suggested it )

[LC0112G]

Didn't get as far as I'd hoped today - took ages to find the old bits, and they needed quite a lot of cleaning. However, results so far...

https://ibb.co/Lkz0pzF
The Hubs are made by KOYO - both the bearings and the cast wheel flange are marked as such.

The ABS reluctor ring has 48 teeth, with an inner diameter of (about) 75mm and an outer diameter of 95mm. Each tooth is 2.5mm wide, and 2.5mm deep.

https://ibb.co/JdBJ3KT
The ABS sensors carry several markings on the wiring side, but these just look like date codes to me. I'll put it under the microscope at work (tomorrow) to see if I can get anything off it.

The sensor tip side looks like this...
https://ibb.co/VvTLPn7

The 'blade' of the sensor is 2mm wide, and 9mm long. It stands 5mm proud of the steering knuckle. The blade is aligned to point towards the hub axle axis. The body/barrel of the sensor is (about) 17mm diameter, and stands about 1.5mm proud of the steering knuckle.

The next step is to assemble the bearing onto the steering knuckle and measure the clearance from the tip of the sensor to the reuctor ring. Unfortunatley I can't do that at home - the surface rust on the knuckle doesn't let the bearing slide on, and I don't have the tools here to 'force it on'. So tomorrow I'll polish up the knuckle/bearing surface and measure it, and then take some 'scope readings of the signal generated by the sensor at various RPM's.

[Doctor Gollum]

Eibach springs drop the car about 30mm from stock.

Alignment numbers are well documented here, but most you can hope for with the rear end adjustment is that the thrust angle is zero and the side to side measurement is even. This is because it has one adjuster that affects both toe and camber.

The Omega isn't a car to try and 'stance'.

[LC0112G]

Buying second hand ,genuine knuckles with genuine ABS sensors would be a way back to working ABS
not cheap though as you'd have to fit them, then get an alignment 

what happened to the original sensors 

I purchased low mile Omega B2 hubs/sensors  as spares when i had omega As (Vauxhall Carltons) years ago 

Yep! New sensors will be ordered. But I think I use the old knuckles, and use some material inbetween to increase the distance if needed.

I don't mind the fitting, as I do all the work on my car myself in my garage. Since I've replaced suspension I'll need an alignment regardless. So that's OK!

The original sensors broke as I tried removing them, while replacing suspension parts. The Haynes book stated to do so, but it would not have been necessary. All of the problems I have with the ABS is just an unlucky side effect from wanting to replace suspension parts.

If you do buy second hand knuckles, think long and hard before you attempt to remove the sensors from them. I have never, repeat NEVER, in about 10 attempts, managed to get one out in one piece. They are always 'welded' in. I suspect its dissimilar metal corrosion - the hub is cast iron, and the shell of the sensor is aluminium. Once water (and salt in the UK) get at it you're stuffed - the things will not come out in one piece if they've been in more than 5 minuites.

[bkorven]

I've found original used knuckles for sale, but I'm thinking about whether they really need replacing or not. I might end up buying them, too.

original used knuckles may well come with original ,working sensors (which is why i suggested it )

That's a great idea. The supply seems to be extremely small, but I did find this LH steering knuckle that has a sensor attached in the image: https://www.ebay.de/itm/352179150061?hash=item51ff835ced:g:pPAAAOSw5UFb~AJX&amdata=enc%3AAQAIAAAAwM7GscXU4moyE%2FNtdssglV6fk9Kp3BdaO%2BEqOFW0w%2BN8NEnj0ZIGYd6NCsycmjacQh8LEh1v%2BIZoKU7zRJMZ%2F7UPD46a3SmxXw82zbrNGPv%2BplHHB3by4GFu%2BxDrgnbv6LmQ%2BzRmwMYfRuOSVZJUqOvi4TuNNC4Wi3pGN5S%2BWtGsAN%2FiYfdUsADoGZccywjXcUBaKZ7H7mmGJWFBhr0pYpTdwKJgWgqRgukCUQY3p%2FLbz5owuEax3wMcwLnp7qWbMg%3D%3D%7Ctkp%3ABk9SR9CNvc7vYg

I could solder it to the wiring of one of my old broken sensors. I guess there is no guarantee the sensor will still be there on the steering knuckle when it arrives, though. Also, there is no guarantee it'll work, ofcourse. The tip of the sensor looks really roughed up.

The same seller also has a RH steering knuckle, without sensor on the image.

The most attractive option from my perspective is to order two new sensors, and install them on my current steering knuckles.

Is there a general agreement on here that it would be a good idea to install new steering knuckles?

If I were convinced that I need new steering knuckles, I'd order both these steering knuckles along with only one new sensor, and give it a try getting the used sensor on the LH steering knuckle to work. But I'm not fond of the idea of finding out the sensor won't work, and having to wait for another separate order to arrive. Nor can I get away from the fact that the bore for the sensor on the used steering knuckles will need sanding, too. A lot of extra work awaits, with the ordering of steering knuckles.

I'm running short of time since I need this car on the road asap to get to work when winter gets here. Preferably several weeks ago. Of course, I do not intend to compromise on safety. Everything will be properly tested.