As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MKE - FLT 1906 - AFTER FLIGHT CREW DEPARTED, THEY NOTICED THE LEFT BLEED AIR FAIL ANNUNCIATOR ILLUMINATED AND STAYED ON. THE RIGHT BLEED AIR FAIL ANNUNCIATOR WAS ALREADY DEFERRED SO THEY TURNED BACK TO MKE. MAINTENANCE COULD NOT DUPLICATE THE LEFT BLEED FAIL, BUT THEY CLEARED THE RIGHT BLEED FAIL MEL BY REPLACING THE RIGHT INSTRUMENT AIR VALVE. (X)