Brake circuit warning light staying on
 

S40 T4 Sport 81,000 miles 2001.

Have just changed the front to rear brake pipes and front passenger brake pipe.(MOT time) Bleed brakes & system ok and have an excellent pedal. Road tested and brakes good just as before any work done
Problem is i now have the "Brake circuit" red warning light staying on the dash display all the time (Handbook position #16). Have checked the brake fluid level and its topped up sitting steady at "max level"
Did a brake bulb check (lights high level light) just in case and all ok plus dash light#8 working correctly, self check goes off as does ABS light dash bulb#10.
The fact ABS light goes off leaving only brake warning on means EBD working fine
What to check next.
Does the brake pedal switch have a set position which has been disturbed from pumping the pedal.??

Will I get any codes if read??

Check the sensor on the fluid resivoir or failing that the hanbrake on warning switch.

Update 13/7 1600hrs:-
Took car to mate who read the codes on his snap-on scanner. Car has no codes showing. Checked the fliud level and still spot on the max mark. Tried disconnecting the battery, reconnected and warning light back on.
Only way we can get warning light to go off is to disconnect the electrical connection located at the bottom of the brake fluid resivoir.
So anybody know how this system works?? Is there a sensor/float/???? located in the bottom of the resivoir?? Hard to explain, even harder to get your hand in!
At no time did the fluid resivoir get low enough to activate the ??? to bring on light
Bit stuck now but want to get to the bottom of this

Cheers

You mention that only way you can get the warning light to go off is to disconnect the electrical connection located at the bottom of the brake fluid reservoir. So my guess would be it has something to do with that. Very silly suggestion, but have you tried removing a little bit of the break fluid liquid. Just a bit to bring it a bit under the max level. Silly but you never know

Floater inside reservoir has a little magnet on inner sides. And the sensor from underneath is practicaly just a reed contact.

There are also two versions of function, depend on car make:

1) Normaly open logic - When fluid level is OK, floater is above reed contact and they are open - light is off. When fluid is low, magnet on floater drops down and makes reed switch conductable - light is on. If you disconnect the wire, light will be off.

2) Normaly closed logic - When fluid level is OK, floater is high enough to reach reed contact and magnet shorts them - light is off. When fluid is low, floater and magnet drops, reed contact goes apart and light is on. If you disconnect wire, light will remain on. So it is reversed logic, no big deal to do it with electronics.

Thanks guys for your info
Update 13/7 2150hrs

Just come in and after reading your message sebaveh it now makes sense. Looking inside reservoir can see a center section with something inside it. It moves from side to side slightly but not up and down. Suspecting that this has stuck and is making reed switch conductable - light is on. When I disconnect the wire, light is off.

Do you know if its a serviceable part, that is I will remove brake reservoir, clean out floater and refit it should then work ok or is it the reed contact will be damaged so buy a replacement??

Can do the work myself ok. (Give it a go first out of curiosity)

What should have been a simple brake replacement job has turned into this But hey that's why we love theses T4'S!!:car:

Update 14/7 1700hrs

Using a syringe removed brake fluid from reservoir. This exposed the floater which lifted out easily. Found some sediment around base, sides of reservoir and on the magnets of the floater which surprised me as they were quite bad. Refilled brake reservoir with fresh fluid. Checked warning light before replacing floater and its was off. Replaced floater and rechecked. Warning light does its self check and then goes OFF!! Success, thanks guys for your help.
:ani-bounce:

silly thought here
if you had enough "gunk" to gum the sensor/float up, perhaps it Might be an idea to flush the system with new clean fluid.

Yep your right Andy that's planned in for w/e. Wont do it any harm
What do you guys recommend Dot 4 , Dot 5 any particular brand?

Dot 4 or 5.1 only.
Do not use Dot 5, as it is totally other chemical substance and can damage all the seals and rubber parts.