As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAXI OUT TO RUNWAY, CAPTAIN PRESSED BRAKES AND BRAKES WENT TO STOPS WITH NO PRESSURE.TROUBLESHOT TO DEFECTIVE PRESSURE SWITCH. REMOVED AND INSTALLED NEW CUSTOMER SUPPLIED SWITCH PER 560 MM 32-42-05 ACCOMPLISHED OPS CHECKS LEAK CHECKS NO DEFECTS NOTED.