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Dodgy Brake Fluid Warning Sensor?


BN Coupe

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This morning the handbrake and 'rear brake lamp' warning lights stayed on, even though the handbrake was off and the brake lamps are all working.  When I got to my garage the warnings mysteriously went off and then came on again.  Mechanic thinks it might be a failed/failing sensor in the brake fluid reservoir - does this sound likely, and if so, where can I get a new sensor from? 

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Very likely the handbrake switch has a oxidised connection or the brake fluid reservoir float sensor is sticking, new brake fluid will solve that. ;)

I would be very surprised if you need a new lid & sensor but do I have a good spare if needed m8y...

 

 

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Thanks for that.  The rear discs and pads were changed not long ago but the invoice doesn't mention fluid.  I'll check with the garage.  The mechanic went straight to the lid of the fluid reservoir, so perhaps it's sticking.  If I need a new one I'll let you know, Stu.  Cheers, Andrew

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It could also be that where the rear pads and discs were changed, some fluid was let out to make room (best practice when retracting the pistons in the calipers of an ABS equipped car) and now the pads have bedded in a bit and adjusted themselves a little that the fluid level in the reservoir has dropped just enough to bring the low level warning light on.

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No warning lights this morning, so whatever was sticking has unstuck itself (Dave, the brake fluid level didn't look low but I'll recheck it.)  I imagine it'll happen again some time, and I'll ignore it.  Part of the joy of running a 17-year-old car.  Having said that, my brother-in-law's 2008 Jetta has had to have an airbag sensor replaced (£180) and a friend's Seat Mii has had to have one replaced under warranty.  Anyway thanks guys.

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43 minutes ago, BN Coupe said:

And the lights are on again... LOL

Mine was intermittent till changed the brake fluid, one thing to note is if the light comes on and your in a position to stop the car and tap the reservoir lid the light will stay on regardless until you shut the car off and re-start it, so you wont know if you made a difference. However if it's the handbrake switch, try releasing & applying it maybe a wiggle :lol: and if the light goes out you know its not the sensor ;)

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I'm pretty sure it's the fluid sensor - there seem to be lots of wires going in to the cap.  If it was the handbrake switch, would the 'rear brake light' warning also be on?

The lights came on again this afternoon when I turned left up a hill, so I'll try not to do that again! :D

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  • The title was changed to Dodgy Brake Fluid Warning Sensor?
  • 4 years later...

I know that this is an old post, but just to give an alternative remedy if the above suggestions didn't fix the warning lamp fault.
I had exactly the same problem a few weeks ago. (Handbrake and Brake Lamp Illuminated). 
I removed the panel covering the nearside rear light cluster. 
Below the light fitting there is a brake lamp sensor, which was quite wet. I'd jet washed the car a few days before and probably got a little over zealous with the Kercher, and water seeped through the boot seal.
Anyway, I removed the sensor (One bolt and disconnect the four pin plug).
I removed the PCB from it's case (carefully), and found it to be really dirty.
I cleaned the solder tracks and areas around the pins with some alcohol, applied with a cotton bud.
Popped the board back into the case and refitted.
This sorted the problem out and it hasn't recurred.

Hope it helps.

 

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