ABS warning light

[bobharford]

Hi
C3 2005 exclusive HD
There is a warning message that the ABS isn't working, is the car safe to drive until I can get it looked at?
Thanks

[MikeT]

Officially speaking, the car is now unfit for public road use - an ABS fault will fail the MOT and should you get a VOSA spot-check while using the car on the road in this condition, could find yourself car-less in the middle of nowhere. You are allowed to drive the car to a pre-booked appointment at a garage of your choice.

Mechanically speaking, the ABS has recognised a fault and as a fail-safe has turned the ECU off meaning your brakes are functional without ABS assistance, so still driveable.

[RichardW]

It's entirely possible that there is no rear brake compensator on this car, so you need to drive carefully, as the rear may lock up under braking, and make a bid to swap ends with the front....

[R9UKE]

I've never understood this ABS issue. There are still plenty of cars on the road without ABS as standard, so surely the ones with faulty ABS are exactly the same and hence perfectly road legal? This obviously isn't the case though...

[RichardW]

Early ABS cars were pretty well the same as non-ABS cars, just with the ABS kit bolted on. Later cars are more developed and have done away with certain items non-ABS cars are fitted with - eg the rear brake compensator (our 03 Picasso doesn't have one) and letting the ABS and / or ESP pick up the pieces. If the ABS is down then you need to be aware of the back locking up, particuarly on light loads - if the back locks up on a downhill stretch, it can quickly overtake the front and roll the car over.

Of course, Xantias wither their superior load compensated pressure operated rear brakes don't suffer this fate

[xantia_v6]

Cars manufactured without ABS either have deliberately weak rear brakes (most vehicles up to the 1970s) (1) or have a compensator valve which reduces the rear braking when there is little load on the rear suspension.

Both these schemes are to avoid rear wheel lock-up which can be a very nasty experience(2).

Hydraulic Citroens (up to and including the Xantia)(3) achieved the same thing with the doseur valve using the pressure in the rear suspension to modulate the rear brakes.

ABS has made such schemes somewhat redundant, so a more modern car might well have too much rear braking for safety when the ABS is not operational.

(1) My e-type has the brake balance fairly finely set so that with the car unladen, all 4 wheels lock at the same time, but when I fitted wider tyres, the extra front grip caused the rear wheels to lock first. The car has a 50-50 weight distribution, but a 70-30 brake balance.

(2) I drove a Talbot horizon with a seized brake compensator (4), and on more than one occasion found myself on a straight road facing the car following me, scary for both parties, on another occasion, negotiating a LH bend, I hit the front RH wheel on the LH kerb (ie spun through 270 degrees), but ended up traveling in the correct direction.

(3) I have mad an emergency stop from high speed in a Xantia with failed ABS, and the dosuer valve prevented rear wheel lockup.

(4) It was a company car and the dealers refused to accept that it had a fault, despite it being presented to them several times, including with bent suspension following a high speed "off" on the A1(M).

[bobharford]

Appreciated drove home and the warning light is now not appearing
Think I will need to get it checked out though

[reblack68]

The weather might have caused a temporary problem in the ABS. I would check that the ABS is working and leave it at that unless the light comes on again.