MOT Rules re dashboard lights.

In message , "Andy Dingley " writes

To be fair to the original poster, she did not complain that the car had failed - she merely asked whether or not failure of the light was cause for automatic MOT failure. Reason for the question was that the car passed the MOT test the previous year, with the same light failure.

I think she now knows the answer :-)

It'll soon be that time of year when I take the ABS fuse out. I do a lot of travelling around Buxton and the peaks so consider myself pretty good in snow but it's a nightmare driving in snow with ABS. From my own tests I can stop in half the distance in snow with the abs disabled. If I had the choice of a car fitted with or without ABS I would choose without.

But in this case the system hasn't turned it self off, it is faulty because it is showing a fault light, maybe the next stage of the failure is to falsely detect a lock up, and release the brakes when it shouldn't. Far more dangerous than not having ABS fitted at all.

Also on some ABS systems, the load sensing valve is left out, so if ABS fails there will be far more tendency to lock up than with a vehicle never fitted with ABS. (mainly commercial vehicle systems)

I agree. Having had the benefit of a three day advanced driving course by ex-police instructors, I have to say that with the amount of practise they gave me with cadence braking - I feel much more secure with "personal "ABS than the terrible feeling of placing it in the hands of the car's ABS................

Indeed. But the same car may not be sold without ABS fitted. Certainly some cars with ABS are designed such that the ABS takes care of the braking. Thus removing the need to forward bias the brakes...

The light will only come on if the controller signals a failure - if it signals a failure, it disables itself and has no control over the braking system. End of.

There is caution, and there is ignorance. A fault in the ABS system is not unsafe, as the unit will disable itself and warn the driver (via the indicator) that it is off, thereby making him aware of the problem and either (a) correcting the fault at the cost of a few hundred quid, or (b) ignoring it and braking the old-fashioned way.

Hellraiser.............>

The ABS constantly checks itself whilst the system is powered - if it goes past a certain number of acceleration/deceleration cycles with no faults reported, the ABS system is enabled. It may have been you had an intermittent sensor which worked for long enough for the system to reset to "all-clear" status, shortly before the ABS kicked in.

Hellraiser..............>

How many more times - IF THE LIGHT IS DISPLAYED THE SYSTEM RECOGNISES IT HAS A FAULT AND HAS DISABLED ITSELF!

Depends - only if they have EBD and only on some Teves systems.

Hellraiser..............>

I guess with 43800 postings listed under Google he goes for quantity rather than quality - or there is an Andy Dingley industry!

What's the insurance position if you do that?

Pretty good considering I've now halved my breaking distance and less likely to hit someone or something in the event of an emergency. Although I suppose I have now increased the risk of being rear-ended by one of the many foolish motorists who rely on ABS and believe that it actually helps them to stop quicker.

Hellraiser ( snipped-for-privacy@blueyonder.co.uk) gurgled happily, sounding much like they were saying :

Not *always* quite that black and white.

I had an iffy front wheel sensor on a CX - moving away after starting, the ABS wouldn't detect it and disable it until speed got up to about 20mph or you braked with the steering other than straight - at that point, the light'd come on.

Before then, braking would be... ummm... entertaining... as the ABS decided you were on ball bearings or sheet ice.

Hellraiser ( snipped-for-privacy@blueyonder.co.uk) gurgled happily, sounding much like they were saying :

Some do, some don't. Many only do the testing on power-on.

And how old was the CX.... A dodgy sensor would most likely require a short distance before a fault condition could be flagged up as the computer needs to compare the inputs off the other 3 sensors before condeming it, most of them have done that by the time you've hit 5MPH anyway. Plus, it was a Citroen :)

Hellraiser..............>

I doubt that with modern ABS systems - it is a recipe for disaster if so. What happens if you are on a long journey and a sensor gives out, then you brake sharply? I would imagine all modern systems run a constant diagnostic, I know the Teves system on my Fiat does and I'd be most worried if others didn't :(

Hellraiser..............>

Hellraiser ( snipped-for-privacy@blueyonder.co.uk) gurgled happily, sounding much like they were saying :

1989. Sure, not exactly current, but you did kinda suggest ALL ABS did what you were suggesting. Not so.

Nothing to do with distance. It was entirely speed and braking-whilst- turning that would trigger the failure mode. As I very nearly terminally found out heading down Long Mynd...

The XM does it before you move off - there's a more intelligent active testing regime.

With Bosch ABS... :)

Hmm. The question was about cars failing MOTs on ABS lights misbehaving. So 'modern ABS systems' might be only a small proportion of the cars out there...

My Fiat is 1998, so it's hardly cutting edge, and the same system is used on a wide variety of cars from that era, ranging from Peugeots to Mercs....

Hellraiser.............>

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Sharon Derben" saying something like:

They're only necessary if you can see Paradise by them.