Brake fail warning light

[Tim]

Nice detective work.

Tim

[SaharaDust]

Appreciate this is an old thread

Recently installed a new front rear split master cylinder along with a new brake fail switch (triangle shape) that screws into body of master cylinder

The brake fail light has come on a couple of times.  After checking for any system leaks and fluid level in master it was time to ponder. So adjusted rear brakes, removed switch from master cylinder and gave a big push on brake pedal.  Start engine and brake fail illuminated prior to oil pressure then lamp goals out.  Lamp stays out.

So does this mean that even though brake system does not have a point of failure the adjustment of the rear brakes may be enough to give a pressure imbalance between front circuits?

So way back when these systems were new and brake fail lamp illuminated the owner might either choose to ignore the lamp or back to dealer.  No wonder dealers went bonkers.

Have searched around a fair bit (not absolutely everywhere) and this thread is the best explanation of how brake fail works.

The float in master cylinder tank a much simpler solution and probably does not require a reset.

Cheers

Cheers