why does the ABS dashboard light illuminate randomly?

[shaunb]

Please can someone assist? I am not sure what the problem is, but he ABS light and and a red warning light come on periodically. This will happen as one starts the car but then other times it does not. It seemed to only be when the car was facing up hill, that it would come on, and if facing down hill it would be off. Recently though, there is no patterns to it and will goes for days without the warnings, then one for 2 to 3 trips. etc.

please help explaion this one. this is for an Audi A4 1.8T 1998

[e6m6a6]

im not sure if your car is the same layout as the mk4 golf but my ABS sensor used to have a fit every now and then, mine turned out to be a dodgy sensor, water was gettin in somewhere as i saw a pattern when it was heavy rain it would light up, a new one from VW was £50 so i changed it over and problem solved

[shaunb]

thank you for the info. this is for am Audi A4 1.8 T 1998 model. there don't seem to be any sensors on the wheels at all. I will price the unit and see from there.

thank you

[Eshrules]

There are no sensors on any of the wheels?

[turbine2]

Could be the sign of a battery starting to drop below optimum. Electricals can start to get funny when that happens in my experience.

[shaunb]

There are no sensors on any of the wheels?

No sensors i can see. trhere are no wires on the brake pads or in vacinity. perhaps there is something inside the caliper piston?????? I am totally clueless as to where to start looking???????

[NickPicks]

No sensors i can see. trhere are no wires on the brake pads or in vacinity. perhaps there is something inside the caliper piston?????? I am totally clueless as to where to start looking???????

The sensors will be in the hub carriers (behind the brake disc and back plate). They point at the hub / CV joint, which has grooves on it, so that the sensor can "see" how fast it's going. If the brakes are applied, and the wheels then move at different speeds, it decides that a wheel has locked, and uses the abs pump to stop it from locking.

You should be able to find a thin wire which usually is alongside the brake pad warning wire, then clipped to the suspension strut and travels down to the ABS sensors.

A fault code read should tell you if a sensor is disconnected.