Any ABS experts? (Update: FIXED!)

[r.welfare]

The 405's ABS is giving me grief.Friday before last, there was torrential rain down the M1. I noticed the brake pedal felt rock hard, and the braking application was pretty uneven.Stopped the car when I got home, and I could hear a rapid ticking from under the bonnet...It was coming from the ABS pump modulator. Removing the 3-pin power plug (or the 30A fuse) stops it, but basically if the plug is re-connected with the fuse in, it chatters away. I disconnected the ABS ECU as well, thinking it might have been that, but it makes no difference. Oddly, with everything connected as normal (and the modulator happily chattering), the ABS warning light goes through it's self check if you turn the ignition on, then extinguishes.According to Autodata, one of the pins is 12v power, one is ground, and the other one (I assume, 'cos I can't work it out from the wiring diagram) must provide the signal to activate the ABS modulation. Putting a multimeter across the pins, I have two with 12 volts, and one with nothing (the ground one).I've had this problem once before - when I bought the car and gave it a rather overzealous underbonnet clean. Drying out the power connector restored normal operation that time, but not this time it seems. The power socket's pins were pretty grimy and covered in green sludge - but I've cleaned this all away with electrical contact cleaner and a nail file. The pins are still a lot duller in colour than those for the other electrical connections, but as it seems to be getting the full 12 volts, I is confused...Any ideas? I've just removed the fuse for now so I have normal (albeit non-ABS) braking, but I suspect the glowing warning light might be a bit much for the Man From The Ministry when I come to get it re-MOT'd in October...and given the general decrepit state of the car, I'm reticent to spend £££ on it.

[CIH]

Pretty sure it'll pass the 'test with the light on so long as it passes the braking efficencey test.

[warren t claim]

Before you put it in for it's MOT swap the ABS light for the airbag light! Simples!

[hennabm]

Pretty sure it'll pass the 'test with the light on so long as it passes the braking efficencey test.

Not so. The ABS warning light must follow the correct sequence to be passed for the test.

[Richard]

Sounds like a question for FCF. If you don't get any joy in the Peugeot section try the Citroen section.

[Milford Cubicle]

Before you put it in for it's MOT swap the ABS light for the airbag light! Simples!

The airbag light on 405s is on the steering wheel, I'm not sure if r.welf's even has an airbag.

[r.welfare]

No airbag on my car.I've posted up on FCF, will wait to see what happens.Searching the net, I wonder if it's a relay at fault - can't seem to find if there is an ABS relay on the 405, and if so, where?

[wilko]

This is pure guesswork, but from your description I doubt there is a relay, I reckon the switching takes place inside the modulator itself using a low current live signal from the control unit to switch the main power on/off, and this switching is jammed on / frigged.

[r.welfare]

Thanks Wilko, that would make sense. Probably old age and/or water ingress into the modulator itself, as I reckon the ECU (which is sited up on the scuttle) seems OK in so far as disconnecting the battery, unplugging the ECU and then reconnecting the battery(and re-inserting the ABS fuse), with the ECU still unplugged, gets the modulator chattering away again.Shame really, as the ECU is probably the cheapest bit, secondhand...

[r.welfare]

OK, I may have a solution here.Reading on t'interweb, I suspect Wilko's analysis of a knackered relay deep within the sealed bowels of the electronics box on the modulator to be my problem.Thankfully, a trawl of eBay identified a fella in Southampton who was breaking an identical car, so for an outlay of 50 notes I now have a replacement modulator complete with electronics, and an ECU.Taking the power lead off my existing modulator and fitting it temporarily to the "new" one provides complete silence, which seems to indicate the relay in the new one is OK (or completely dead - time will tell).So - my new question - what's the easiest way to undo the metal brake pipes (6 in total - one for each wheel and 2 to/from the master cylinder) going into the modulator that's currently on the car? Mateyboy told me that "you'll never get 'em off", and he had just cut through the ones from the scrap car. So I had a go at removing the pipe stubs from the "new" unit last night. Sure enough, an open-ended 11mm spanner wanted to just round the nuts off, and in the end I had to resort to getting the ring of the spanner threaded over each pipe stub onto the nut, then hitting the spanner with a lump hammer to start the process. All six are now off, no damage to the threads into the modulator and I have cleaned everything up.This is obviously not an option for the unit in the car, as I'd prefer to keep the brake lines in one piece! Some people recommend a soaking of the nuts in WD-40 or vinegar, while others advocate the heat approach - but I'd rather not do that due to the electronics (not to mention the fuel lines and headlight) nearby! I've ordered a brake pipe spanner - basically a six-sided ring with a small cut in one end to slip over the pipe - are they any good? It might not arrive before tomorrow when I'd like to have a go at doing this, so are there any other alternatives to use, e.g. molegrips, stilsons etc?

[ashmicro]

This is obviously not an option for the unit in the car, as I'd prefer to keep the brake lines in one piece! Some people recommend a soaking of the nuts in WD-40 or vinegar, while others advocate the heat approach - but I'd rather not do that due to the electronics (not to mention the fuel lines and headlight) nearby! I've ordered a brake pipe spanner - basically a six-sided ring with a small cut in one end to slip over the pipe - are they any good? It might not arrive before tomorrow when I'd like to have a go at doing this, so are there any other alternatives to use, e.g. molegrips, stilsons etc?

Plusgas, Comma Releasing Oil spray (thinner than WD40) or Glock gun oil.And yup, brake spanners are the very job for the job. Mole Grips FTL in this type of situation.

[VWPowered]

i just had to replace both front hubs (one with a broken wheel bolt, other with a mullered bearing) and broke the abs sensor, just ordered another but brakes seen to work spot on but the abs light stays on, after much donkeying around with french breakers yard keep giving me wrong parts i'd lost faith...wrong driveshaft, wrong this and that, makes me annoyed...now all good finally just the turbo to sort out, is there noooo end

[CIH]

last resort; mole grips

[r.welfare]

No need for mole grips - after three hours of spannering and swearing (although in fairness an hour was spent bleeding the brakes again), I CAN HAZ ABS!I gave the brake pipe unions into the ABS unit periodic dousings of WD40 over the last 24 hours and all, apart from one, came out fine. My Draper brake pipe spanner began rounding the last one off to begin with, but once I managed to remove the pump from it's brackets, I could move it so I could get the spanner onto some unrounded flats. Lots of fun getting the threads to bite on the way back in, though.The brake pedal is a bit more spongy than before - I suspect there may still be a little air somewhere in the system, as it drained the reservoir from the pipes fairly rapidly when I undid it - but the brakes are definitely still there, and the ABS cuts in on a panic stop no bother. ABS light behaves itself, too. For £50, that's a bit of a result, and (hopefully - fingers crossed nothing else major goes wrong) will mean there's nothing too much to vex the MOT man come October. I'll definitely have another go at bleeding it before then, mind.

[Milford Cubicle]

Good work, no need for the non-ABS hubs from my 405 baler then.