Brake warning light

[Rpmayne 0]

Without fail I get rid of one problem and another arises...

 

Brake warning light beneath the clocks. After a few minutes of driving it flickers then comes on, and does go out sometimes intermittently. When I put my foot on the brake it turns off, and when I release it it comes back on again.

 

Fluid is ok, tried unplugging the cap switch and it made no difference. When it is off the handbrake operates the light as normal so don't think its that.

 

Any ideas?

[camper driver 0]

If its the ABS warning light thats coming on. First port of call would be to check the abs sensors, Theres one on each of the front brakes.

[Rpmayne 0]

It's the red LED on the dash which usually only comes on when the handbrake is on. Still flickering but didn't stay on as much this morning. Just don't understand why pressing the brake pedal would turn it off, unless its a master cylinder pressure problem.

 

ABS light works as normal.

[dinkus 10]

Every wheel has an ABS sensor on it - it's a 7cm or so ring with slots in it and a magnet that points at it. If that ring gets crud stuck in it, or corrodes too much or gets bent out of shape - you'll get the ABS light on.

 

If you plug the car into VAG-COM then the car will tell you where it thinks the problem is and gives you a starting point to fix it :)

[GIXXERUK 0]

abs ring :-) and sensor on the rear (did my discs, pads, bearings the other day)

[GIXXERUK 0]

It's the red LED on the dash which usually only comes on when the handbrake is on. Still flickering but didn't stay on as much this morning. Just don't understand why pressing the brake pedal would turn it off, unless its a master cylinder pressure problem.

 

ABS light works as normal.

 

doh! just read this :-) iirc this will come on for the handbrake and indicate a low fluid level in the master cylinder

pull the lid and see if it comes on , then check the wires and float , i'm not sure it may also come as a wear indicator for low brake pads

 

hth

[Roger Blassberg 0]

It sounds like a problem with either the float switch or the float itself in the master cylinder/fluid reservoir.

 

If the level of fluid is correct, the float may still be too low if it has a puncture - see if it has any fluid in it. The light may go out under braking because the brake fluid sloshes about and affects the level.

 

If the switch is intermittently faulty it may cause the flicker - check the connections to the switch and clean then with a proprietary contact cleaner. If none of these cures the problem, check the wiring to the fluid reservoir switch.

 

If that doesn't cure it you may need to change the switch (not sure if that entails replacement of the reservoir too).

 

Best wishes

 

RB

[Rpmayne 0]

Cheers all. Tried disconnecting the brake fluid plug completely and the light stayed on, then when driving it started to flicker again. Haven't buzzed the reservoir switch through yet but its looking like that may not be the cause.

 

When the light is on, pulling the handbrake makes it come on a touch brighter. Think that switch is ok and the visible wiring from the reservoir looks ok. Suppose checking things at the fuse box is the next step.. :(

[stevie_f_2004 0]

Could the sensor be wet/damp...previous posts show this as a cause of this light coming on....happened to me recently during the bad weather spell Stuck it inthe garage for a week all dried out and no return of the dim light!!!

[Rpmayne 0]

Alright all, still having problems with this brake warning LED and the following is confusing me even more now:

 

Recently it hadn't beem coming on. I have already ruled out the level switch and handbrake switches by disconnecting, linking out etc.

 

Yesterday I booted it and the LED starting coming on, intermittently at first but by the end of the trip constant. However, when the brake pedal is pushed the LED goes out.

 

I sat on the drive with the engine stopped but ignition on. With the LED on, whenever I pressed the brake pedal the LED went out, a relay clicked, a wirring noise could be heard and the main lights dipped very slightly. By trial and error I've found the fuel pump relay (12) was being switched.

 

With the fuel pump relay removed the LED stays off and everything seems normal. Plug it back in and the above symptoms reoccur.

 

I've been trying to follow the wiring diagrams and can't get my head around how these things can be linked. Can only assume there must be something shorting behind the fuseboard, or the board itself is faulty.

 

Any thoughts??

[Supercharged 2]

Weird - try a new FP relay - could just be a bad earth..

[Andi 2,147,483,647]

The wiring to the fuel pump relay is more likely the cause, it gets a dodgy earth in the wiring behind it.

Try changing the relay, but I think it'll be the wiring upto the board that the relay plugs into. Perhaps an earth it shorting from the brakes somewhere to the fuel pump relay?

 

The fuel pump relay will only trigger when it receives an earth signal from the ECU. If it gets that signal from somewhere else, it would trigger it also.

 

Not sure how this would make your brake indicator light come on though.

Maybe more drain on the electrical system? Dunno..

[Rpmayne 0]

Thanks, I'll try swapping the relay over and look at the loom going back to the fuel pump tonight.

[Henny 0]

anyone thought about the possibility of the brake pad wear sensors being the problem? :roll: :lol:

 

Check in your front wheel arches where the bottom of the suspension strut attaches to the hub. You should find:

 

No cables = no ABS and no wear sensors (if this is the case, ignore me!)

1 cable = ABS OR wear sensors (not sure if wear sensors were fitted without ABS though)

2 calbes = ABS and wear sensors...

 

I've seen a few cars where the pads have been replaced with the cheaper (and usually longer lasting!) non-sensor pads so the wear sensor cables have just been left dangling in the wheel arch (front only!). Over time, the dangling cable catches on the suspension and wheel as it moves and damages the insulation. When the damaged cable touches something metal it lights up the little red light on the dash board to alert the driver that their pads are wearing low... Brake, the cable moves and stops making contact, and the light goes out... ;)

 

Hope this helps... 8)

 

EDIT: Oh, and as an afterthought, if the sensor wires ARE damaged and the engine being off on your drive, you may well be back-feeding power to the fuel pump relay which will cause it to fire the fuel pump... would explain that fault too... ;)

[Andi 2,147,483,647]

Henny, how would that cause the fuel pump relay to fire up?

[Henny 0]

see edit...

[Rpmayne 0]

I didn't get much of a chance to have a look last night so will be friday afternoon now, took me longer than I thought to get the heater controls and centre console back in. Have left the drivers side all exposed to check the fusebox / cabling though.

 

I do have ABS but not sure about the brake pad wear cables. Have changed the pads a few times now and have never noticed, will try taking a wheel off and looking before tackling the fuse box again.

 

Thanks.

[Rpmayne 0]

I had a look under the car this lunchtime and my car (early '94) only has the ABS sensor cable, nothing for brake pad wear. Pads are in pretty good condition aswell.

 

The fuel pump relay does feel hot compared to all the other relays.

[Rpmayne 0]

I finally had a good go at this problem at the weekend, spent 9 hours doing the following to try and figure out why the brake light was intermittently coming on.

 

- Unplugged all the fusebox connectors and had a good look behind. Found a few very dodgy alarm connections which I repaired but nothing seemingly related to the brake light. The main alarm feed cut into the fusebox wire had a loose solder joint.

 

- Replaced the fusebox with a second hand one of the same part number. Thought it maybe something internal to the board.

 

- Replaced the fuel pump relay with a second hand one.

 

As I expected this hasn't solve all my problems. The brake light hasn't come on since (haven't driven far) but now everytime the brake pedal is pushed with the engine off the fuel pump primes. Turning the light switch from off to dipped to full also primes the pump. Once the car is running the ECU earthes the fuel pump relay and holds it on, so not really a running problem, just abit worrying that something is wrong somewhere.

 

I have no idea how these things are related. All I can think is either something is shorting the ECU signal to the fuel pump to ground, or the supply is being lost when using the brake / light switch so it re-initialises.

 

Any help much appreciated as always.

[Dranoel4a 0]

did you ever work this out. i've got the same sort of problem would appreciate any light you can shine on it.

 

leo