ABS light...

[LR5V]

It may be half term & you are off duty, but I hope the subject you teach isn't English! 

I wouldn't go too cheap with the sensors, the lower quality ones have really poor quality plastic bodies that just snap off, making them a lot harder to get out.
Great as GSF are... from my experience their unknown or non branded stuff does tend to be not that great
-I would stick to known brand.

The advice about swapping the rear sensors over to see if the fault follows the sensor is really good for diagnosing if the ABS ecu is broken.
Where the wheel sensors connect to the ECU the solder goes dry and cracks at the circuit board. it is possible to re-solder these terminals, but getting to them involves opening the case and this is a right pita to do without destroying it.
If the ECU is broken I would suggest sending it to BBA Remen, iirc they will fix it for £150 and it will come back to you with a lifetime warranty.
I don't think it has been mentioned that apart from people breaking the warning bulbs deliberately to hide the fault, the other thing bad owners do is just ignore the light and the bulb just burns out, the majority of Mk3 I find in scap yards the bulbs are burnt out.
lastly, the warning light will not re-set its self, the fault has to be cleared.
Good luck, I hope its just the sensors.

[Gti_Jamo]

These pumps don't like manky old brake fluid either and it can become contaminated with water. I've took a few of them apart and cleaned them out and they have worked fine. Don't really need vagcom to bleed the system either. As for sensors, I've used cheaper ones and they have worked fine but as already mentioned the're not as robust as oem parts and can fail prematurely. You can manually check the resistances of the sensors with a multimeter at the connectors or if it's an early Mk3 they can easily be checked via the abs ecu under the panel on the passenger footwell if you have the appropriate wiring diagram.

[VW BUSH]

These pumps don't like manky old brake fluid either and it can become contaminated with water. I've took a few of them apart and cleaned them out and they have worked fine. Don't really need vagcom to bleed the system either. As for sensors, I've used cheaper ones and they have worked fine but as already mentioned the're not as robust as oem parts and can fail prematurely. You can manually check the resistances of the sensors with a multimeter at the connectors or if it's an early Mk3 they can easily be checked via the abs ecu under the panel on the passenger footwell if you have the appropriate wiring diagram.

I get round using vag com by locking up on the gravel drive running the pump and then bleeding as normal.
you can get away with just normal bleeding but I have had it where I needed to run the pump via VC.
The plastic bodied sensors are all gash, dont think you can get the metal ones anymore.
Problem is when they are dry/cold they measure in normal limits then bum out in use giving you the pedal vibe and default brakes when you least expect it.
you can take a chance but I always change sensors in pairs minimum and write it on the inner wing with a china graph.

Best tip is to drill the hole out they go into and skim the scale out to fresh metal, about 0.6mm bigger is fine.
The sensor goes in with no force, the plastic does not waist and crack when it swells and you can change them easier next time

[lectrotek]

Think i''ll be doing that. Cheers 

[lectrotek]

So the front sensors were sorted nice and easy.

rear ones, another matter. couldn't get the body of the sensor oiut of the hole for love nor money. most of the sensor is out but there's still some remainder left in the hole. going to have to admit defeat and book it in somewhere.

odd thing is...i wiped the 9 faults and re-scanned after replacing the front sensors and the fault count went down to 5, but of those 5, there were still two faults for the front sensors!

weird.

[LR5V]

I am afraid that is bad news - your ABS ecu is damaged, likely to be dry solder joints.

It is possible to remove the ecu from the pump without spilling brake fluid or letting air into the system, its only four tiny male torx head bolts on the underside of the ecu, some slight bending of brake pipes and it will slide off

Getting to the stuck part of the rear sensors is not that difficult - removing the caliper carriers, remove centre bearing dust cap, remove split pin & cage, undo nut and the disk just pulls off leaving the stub axle with the stuck sensor ready to be pulled with pliers or drifted through. The hardest part is adjusting the bearing properly for the correct amount of play.

[SimonG]

Yep, dry solder joints on the PCB inside. If you are confident, unbolt the ECU from the pump and open it up. It's a toughie to do because it's all sealed up. There is a good guide on Club GTI and this is what I have done. Otherwise it's looking for a good second replacement or sending it off to BBA Reman who would be able to repair it.

If you do look for a replacement one make a note of the ECU part number, it's printed on it and only replace with the same part number.